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	$68.47	4.134%	$71.3005	$71.30	$71.30	$71.30
Purchase #2	$228.69	13.122%	$258.6987	$258.70	$258.70	$258.70
Purchase #3	$18.94	11.637%	$21.144	$21.14	$21.15	$21.10
Purchase #4	$43.84	10.112%	$48.2731	$48.27	$48.25	$48.30
Purchase #5	$79.97	12.184%	$89.7135	$89.71	$89.70	$89.70
Purchase #6	$61.80	6.409%	$65.7608	$65.76	$65.75	$65.80
Purchase #7	$65.59	7.856%	$70.7428	$70.74	$70.75	$70.70
7 purchase totals =	$567.30		$625.6334	$625.62	$625.60	$625.60