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	$46.90	12.696%	$52.8544	$52.85	$52.85	$52.90
Purchase #2	$174.69	12.364%	$196.2887	$196.29	$196.30	$196.30
Purchase #3	$250.55	13.676%	$284.8152	$284.82	$284.80	$284.80
Purchase #4	$110.34	9.276%	$120.5751	$120.58	$120.60	$120.60
Purchase #5	$114.73	12.761%	$129.3707	$129.37	$129.35	$129.40
Purchase #6	$62.49	3.696%	$64.7996	$64.80	$64.80	$64.80
Purchase #7	$236.61	10.109%	$260.5289	$260.53	$260.55	$260.50
7 purchase totals =	$996.31		$1,109.2326	$1,109.24	$1,109.25	$1,109.30