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	$42.36	5.606%	$44.7347	$44.73	$44.75	$44.70
Purchase #2	$133.50	13.723%	$151.8202	$151.82	$151.80	$151.80
Purchase #3	$172.63	4.183%	$179.8511	$179.85	$179.85	$179.90
Purchase #4	$211.85	11.715%	$236.6682	$236.67	$236.65	$236.70
Purchase #5	$84.95	6.343%	$90.3384	$90.34	$90.35	$90.30
Purchase #6	$206.82	12.401%	$232.4677	$232.47	$232.45	$232.50
Purchase #7	$118.31	7.710%	$127.4317	$127.43	$127.45	$127.40
7 purchase totals =	$970.42		$1,063.3120	$1,063.31	$1,063.30	$1,063.30