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	$112.66	12.108%	$126.3009	$126.30	$126.30	$126.30
Purchase #2	$51.35	6.469%	$54.6718	$54.67	$54.65	$54.70
Purchase #3	$77.88	10.388%	$85.9702	$85.97	$85.95	$86.00
Purchase #4	$140.88	12.315%	$158.2294	$158.23	$158.25	$158.20
Purchase #5	$109.92	3.767%	$114.0607	$114.06	$114.05	$114.10
Purchase #6	$245.42	7.377%	$263.5246	$263.52	$263.50	$263.50
Purchase #7	$82.28	10.412%	$90.847	$90.85	$90.85	$90.80
7 purchase totals =	$820.39		$893.6046	$893.60	$893.55	$893.60