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	$103.36	5.210%	$108.7451	$108.75	$108.75	$108.70
Purchase #2	$133.33	8.371%	$144.4911	$144.49	$144.50	$144.50
Purchase #3	$203.26	9.237%	$222.0351	$222.04	$222.05	$222.00
Purchase #4	$229.44	8.227%	$248.316	$248.32	$248.30	$248.30
Purchase #5	$47.47	7.212%	$50.8935	$50.89	$50.90	$50.90
Purchase #6	$76.75	12.513%	$86.3537	$86.35	$86.35	$86.40
Purchase #7	$203.78	9.158%	$222.4422	$222.44	$222.45	$222.40
7 purchase totals =	$997.39		$1,083.2767	$1,083.28	$1,083.30	$1,083.20