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	$75.35	9.370%	$82.4103	$82.41	$82.40	$82.40
Purchase #2	$111.30	10.350%	$122.8196	$122.82	$122.80	$122.80
Purchase #3	$196.46	6.613%	$209.4519	$209.45	$209.45	$209.50
Purchase #4	$88.84	11.785%	$99.3098	$99.31	$99.30	$99.30
Purchase #5	$182.37	3.366%	$188.5086	$188.51	$188.50	$188.50
Purchase #6	$96.26	12.432%	$108.227	$108.23	$108.25	$108.20
Purchase #7	$182.56	9.717%	$200.2994	$200.30	$200.30	$200.30
7 purchase totals =	$933.14		$1,011.0266	$1,011.03	$1,011.00	$1,011.00