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	$201.36	5.712%	$212.8617	$212.86	$212.85	$212.90
Purchase #2	$67.33	4.792%	$70.5565	$70.56	$70.55	$70.60
Purchase #3	$236.57	4.139%	$246.3616	$246.36	$246.35	$246.40
Purchase #4	$92.90	13.168%	$105.1331	$105.13	$105.15	$105.10
Purchase #5	$142.52	9.272%	$155.7345	$155.73	$155.75	$155.70
Purchase #6	$83.53	6.811%	$89.2192	$89.22	$89.20	$89.20
Purchase #7	$219.81	12.771%	$247.8819	$247.88	$247.90	$247.90
7 purchase totals =	$1,044.02		$1,127.7485	$1,127.74	$1,127.75	$1,127.80