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	$101.93	9.736%	$111.8539	$111.85	$111.85	$111.90
Purchase #2	$36.54	5.120%	$38.4108	$38.41	$38.40	$38.40
Purchase #3	$90.45	9.613%	$99.145	$99.15	$99.15	$99.10
Purchase #4	$170.70	4.642%	$178.6239	$178.62	$178.60	$178.60
Purchase #5	$229.99	13.791%	$261.7079	$261.71	$261.70	$261.70
Purchase #6	$34.56	7.454%	$37.1361	$37.14	$37.15	$37.10
Purchase #7	$135.51	10.781%	$150.1193	$150.12	$150.10	$150.10
7 purchase totals =	$799.68		$876.9969	$877.00	$876.95	$876.90