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	$219.27	7.116%	$234.8733	$234.87	$234.85	$234.90
Purchase #2	$74.69	11.846%	$83.5378	$83.54	$83.55	$83.50
Purchase #3	$227.85	7.279%	$244.4352	$244.44	$244.45	$244.40
Purchase #4	$118.86	8.148%	$128.5447	$128.54	$128.55	$128.50
Purchase #5	$36.27	12.803%	$40.9136	$40.91	$40.90	$40.90
Purchase #6	$124.63	8.275%	$134.9431	$134.94	$134.95	$134.90
Purchase #7	$144.56	7.164%	$154.9163	$154.92	$154.90	$154.90
7 purchase totals =	$946.13		$1,022.1640	$1,022.16	$1,022.15	$1,022.00