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	$210.87	8.163%	$228.0833	$228.08	$228.10	$228.10
Purchase #2	$55.27	11.809%	$61.7968	$61.80	$61.80	$61.80
Purchase #3	$122.79	4.683%	$128.5403	$128.54	$128.55	$128.50
Purchase #4	$37.83	9.805%	$41.5392	$41.54	$41.55	$41.50
Purchase #5	$139.85	5.742%	$147.8802	$147.88	$147.90	$147.90
Purchase #6	$125.49	9.466%	$137.3689	$137.37	$137.35	$137.40
Purchase #7	$120.56	9.419%	$131.9155	$131.92	$131.90	$131.90
7 purchase totals =	$812.66		$877.1242	$877.13	$877.15	$877.10