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	$81.42	13.873%	$92.7154	$92.72	$92.70	$92.70
Purchase #2	$33.27	13.398%	$37.7275	$37.73	$37.75	$37.70
Purchase #3	$59.80	12.696%	$67.3922	$67.39	$67.40	$67.40
Purchase #4	$97.44	4.172%	$101.5052	$101.51	$101.50	$101.50
Purchase #5	$159.29	9.185%	$173.9208	$173.92	$173.90	$173.90
Purchase #6	$26.67	6.115%	$28.3009	$28.30	$28.30	$28.30
Purchase #7	$249.27	10.355%	$275.0819	$275.08	$275.10	$275.10
7 purchase totals =	$707.16		$776.6439	$776.65	$776.65	$776.60