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	$52.36	12.778%	$59.0506	$59.05	$59.05	$59.10
Purchase #2	$55.64	10.204%	$61.3175	$61.32	$61.30	$61.30
Purchase #3	$201.33	6.781%	$214.9822	$214.98	$215.00	$215.00
Purchase #4	$244.62	4.676%	$256.0584	$256.06	$256.05	$256.10
Purchase #5	$7.65	5.135%	$8.0428	$8.04	$8.05	$8.00
Purchase #6	$241.93	5.497%	$255.2289	$255.23	$255.25	$255.20
Purchase #7	$188.85	9.644%	$207.0627	$207.06	$207.05	$207.10
7 purchase totals =	$992.38		$1,061.7431	$1,061.74	$1,061.75	$1,061.80