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	$41.71	11.152%	$46.3615	$46.36	$46.35	$46.40
Purchase #2	$6.52	12.330%	$7.3239	$7.32	$7.30	$7.30
Purchase #3	$243.38	11.143%	$270.4998	$270.50	$270.50	$270.50
Purchase #4	$71.71	11.348%	$79.8477	$79.85	$79.85	$79.80
Purchase #5	$18.73	9.418%	$20.494	$20.49	$20.50	$20.50
Purchase #6	$108.79	9.821%	$119.4743	$119.47	$119.45	$119.50
Purchase #7	$52.78	9.640%	$57.868	$57.87	$57.85	$57.90
7 purchase totals =	$543.62		$601.8692	$601.86	$601.80	$601.90