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	$12.53	12.732%	$14.1253	$14.13	$14.15	$14.10
Purchase #2	$184.93	3.129%	$190.7165	$190.72	$190.70	$190.70
Purchase #3	$222.54	12.707%	$250.8182	$250.82	$250.80	$250.80
Purchase #4	$128.93	4.679%	$134.9626	$134.96	$134.95	$135.00
Purchase #5	$187.65	4.566%	$196.2181	$196.22	$196.20	$196.20
Purchase #6	$186.57	9.752%	$204.7643	$204.76	$204.75	$204.80
Purchase #7	$137.47	11.266%	$152.9574	$152.96	$152.95	$153.00
7 purchase totals =	$1,060.62		$1,144.5624	$1,144.57	$1,144.50	$1,144.60