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	$104.46	5.421%	$110.1228	$110.12	$110.10	$110.10
Purchase #2	$93.88	9.568%	$102.8624	$102.86	$102.85	$102.90
Purchase #3	$175.47	9.140%	$191.508	$191.51	$191.50	$191.50
Purchase #4	$128.28	4.628%	$134.2168	$134.22	$134.20	$134.20
Purchase #5	$191.50	12.873%	$216.1518	$216.15	$216.15	$216.20
Purchase #6	$130.82	6.364%	$139.1454	$139.15	$139.15	$139.10
Purchase #7	$198.57	9.344%	$217.1244	$217.12	$217.10	$217.10
7 purchase totals =	$1,022.98		$1,111.1316	$1,111.13	$1,111.05	$1,111.10