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	$83.46	6.434%	$88.8298	$88.83	$88.85	$88.80
Purchase #2	$136.45	12.523%	$153.5376	$153.54	$153.55	$153.50
Purchase #3	$230.36	5.793%	$243.7048	$243.70	$243.70	$243.70
Purchase #4	$194.25	4.613%	$203.2108	$203.21	$203.20	$203.20
Purchase #5	$203.82	9.351%	$222.8792	$222.88	$222.90	$222.90
Purchase #6	$131.33	8.563%	$142.5758	$142.58	$142.60	$142.60
Purchase #7	$37.53	13.645%	$42.651	$42.65	$42.65	$42.70
7 purchase totals =	$1,017.20		$1,097.3890	$1,097.39	$1,097.45	$1,097.40