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	$53.72	12.163%	$60.254	$60.25	$60.25	$60.30
Purchase #2	$94.47	5.453%	$99.6214	$99.62	$99.60	$99.60
Purchase #3	$115.45	13.242%	$130.7379	$130.74	$130.75	$130.70
Purchase #4	$70.69	7.643%	$76.0928	$76.09	$76.10	$76.10
Purchase #5	$35.38	5.608%	$37.3641	$37.36	$37.35	$37.40
Purchase #6	$66.28	7.295%	$71.1151	$71.12	$71.10	$71.10
Purchase #7	$37.61	9.365%	$41.1322	$41.13	$41.15	$41.10
7 purchase totals =	$473.60		$516.3175	$516.31	$516.30	$516.30