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	$42.66	6.196%	$45.3032	$45.30	$45.30	$45.30
Purchase #2	$82.68	6.692%	$88.2129	$88.21	$88.20	$88.20
Purchase #3	$169.72	5.592%	$179.2107	$179.21	$179.20	$179.20
Purchase #4	$72.52	8.612%	$78.7654	$78.77	$78.75	$78.80
Purchase #5	$160.71	3.634%	$166.5502	$166.55	$166.55	$166.60
Purchase #6	$227.82	5.393%	$240.1063	$240.11	$240.10	$240.10
Purchase #7	$194.40	10.481%	$214.7751	$214.78	$214.80	$214.80
7 purchase totals =	$950.51		$1,012.9238	$1,012.93	$1,012.90	$1,013.00