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	$172.91	11.263%	$192.3849	$192.38	$192.40	$192.40
Purchase #2	$116.85	10.314%	$128.9019	$128.90	$128.90	$128.90
Purchase #3	$139.94	8.635%	$152.0238	$152.02	$152.00	$152.00
Purchase #4	$79.65	13.327%	$90.265	$90.27	$90.25	$90.30
Purchase #5	$56.58	7.165%	$60.634	$60.63	$60.65	$60.60
Purchase #6	$218.98	13.373%	$248.2642	$248.26	$248.25	$248.30
Purchase #7	$174.72	7.773%	$188.301	$188.30	$188.30	$188.30
7 purchase totals =	$959.63		$1,060.7748	$1,060.76	$1,060.75	$1,060.80