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	$175.89	12.154%	$197.2677	$197.27	$197.25	$197.30
Purchase #2	$179.49	5.847%	$189.9848	$189.98	$190.00	$190.00
Purchase #3	$92.48	4.120%	$96.2902	$96.29	$96.30	$96.30
Purchase #4	$37.26	11.191%	$41.4298	$41.43	$41.45	$41.40
Purchase #5	$79.77	11.696%	$89.0999	$89.10	$89.10	$89.10
Purchase #6	$49.81	5.117%	$52.3588	$52.36	$52.35	$52.40
Purchase #7	$209.68	6.165%	$222.6068	$222.61	$222.60	$222.60
7 purchase totals =	$824.38		$889.0380	$889.04	$889.05	$889.10