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	$201.85	10.820%	$223.6902	$223.69	$223.70	$223.70
Purchase #2	$166.29	5.409%	$175.2846	$175.28	$175.30	$175.30
Purchase #3	$175.99	10.111%	$193.7843	$193.78	$193.80	$193.80
Purchase #4	$136.48	5.811%	$144.4109	$144.41	$144.40	$144.40
Purchase #5	$91.43	10.617%	$101.1371	$101.14	$101.15	$101.10
Purchase #6	$142.64	10.793%	$158.0351	$158.04	$158.05	$158.00
Purchase #7	$147.64	4.526%	$154.3222	$154.32	$154.30	$154.30
7 purchase totals =	$1,062.32		$1,150.6644	$1,150.66	$1,150.70	$1,150.60