Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$100.82	11.416%	$112.3296	$112.33	$112.35	$112.30
Purchase #2	$152.31	11.537%	$169.882	$169.88	$169.90	$169.90
Purchase #3	$250.41	8.443%	$271.5521	$271.55	$271.55	$271.60
Purchase #4	$97.34	12.230%	$109.2447	$109.24	$109.25	$109.20
Purchase #5	$221.96	3.226%	$229.1204	$229.12	$229.10	$229.10
Purchase #6	$151.70	12.630%	$170.8597	$170.86	$170.85	$170.90
Purchase #7	$102.48	9.149%	$111.8559	$111.86	$111.85	$111.90
7 purchase totals =	$1,077.02		$1,174.8444	$1,174.84	$1,174.85	$1,174.90