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	$243.44	7.596%	$261.9317	$261.93	$261.95	$261.90
Purchase #2	$190.59	10.487%	$210.5772	$210.58	$210.60	$210.60
Purchase #3	$38.66	4.532%	$40.4121	$40.41	$40.40	$40.40
Purchase #4	$141.54	6.551%	$150.8123	$150.81	$150.80	$150.80
Purchase #5	$55.82	11.702%	$62.3521	$62.35	$62.35	$62.40
Purchase #6	$133.91	13.738%	$152.3066	$152.31	$152.30	$152.30
Purchase #7	$222.96	12.359%	$250.5156	$250.52	$250.50	$250.50
7 purchase totals =	$1,026.92		$1,128.9076	$1,128.91	$1,128.90	$1,128.90