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	$240.44	4.873%	$252.1566	$252.16	$252.15	$252.20
Purchase #2	$209.39	11.491%	$233.451	$233.45	$233.45	$233.50
Purchase #3	$134.40	4.498%	$140.4453	$140.45	$140.45	$140.40
Purchase #4	$104.44	6.190%	$110.9048	$110.90	$110.90	$110.90
Purchase #5	$56.93	8.252%	$61.6279	$61.63	$61.65	$61.60
Purchase #6	$172.83	13.585%	$196.309	$196.31	$196.30	$196.30
Purchase #7	$209.88	11.796%	$234.6374	$234.64	$234.65	$234.60
7 purchase totals =	$1,128.31		$1,229.5320	$1,229.54	$1,229.55	$1,229.50