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	$209.76	13.723%	$238.5454	$238.55	$238.55	$238.50
Purchase #2	$93.27	6.377%	$99.2178	$99.22	$99.20	$99.20
Purchase #3	$176.87	4.685%	$185.1564	$185.16	$185.15	$185.20
Purchase #4	$189.77	5.707%	$200.6002	$200.60	$200.60	$200.60
Purchase #5	$150.47	10.707%	$166.5808	$166.58	$166.60	$166.60
Purchase #6	$152.82	10.799%	$169.323	$169.32	$169.30	$169.30
Purchase #7	$170.59	10.627%	$188.7186	$188.72	$188.70	$188.70
7 purchase totals =	$1,143.55		$1,248.1422	$1,248.15	$1,248.10	$1,248.10