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	$152.98	4.268%	$159.5092	$159.51	$159.50	$159.50
Purchase #2	$65.56	8.510%	$71.1392	$71.14	$71.15	$71.10
Purchase #3	$120.25	5.726%	$127.1355	$127.14	$127.15	$127.10
Purchase #4	$184.36	12.315%	$207.0639	$207.06	$207.05	$207.10
Purchase #5	$171.25	7.356%	$183.8472	$183.85	$183.85	$183.80
Purchase #6	$86.92	8.674%	$94.4594	$94.46	$94.45	$94.50
Purchase #7	$139.92	13.253%	$158.4636	$158.46	$158.45	$158.50
7 purchase totals =	$921.24		$1,001.6180	$1,001.62	$1,001.60	$1,001.60