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	$88.73	3.359%	$91.7104	$91.71	$91.70	$91.70
Purchase #2	$76.93	7.757%	$82.8975	$82.90	$82.90	$82.90
Purchase #3	$108.61	8.716%	$118.0764	$118.08	$118.10	$118.10
Purchase #4	$179.52	8.575%	$194.9138	$194.91	$194.90	$194.90
Purchase #5	$248.27	9.312%	$271.3889	$271.39	$271.40	$271.40
Purchase #6	$10.46	8.216%	$11.3194	$11.32	$11.30	$11.30
Purchase #7	$229.98	11.440%	$256.2897	$256.29	$256.30	$256.30
7 purchase totals =	$942.50		$1,026.5961	$1,026.60	$1,026.60	$1,026.60