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	$213.57	11.711%	$238.5812	$238.58	$238.60	$238.60
Purchase #2	$236.61	9.219%	$258.4231	$258.42	$258.40	$258.40
Purchase #3	$204.95	4.490%	$214.1523	$214.15	$214.15	$214.20
Purchase #4	$216.26	3.274%	$223.3404	$223.34	$223.35	$223.30
Purchase #5	$86.72	4.757%	$90.8453	$90.85	$90.85	$90.80
Purchase #6	$42.83	6.354%	$45.5514	$45.55	$45.55	$45.60
Purchase #7	$201.52	6.374%	$214.3649	$214.36	$214.35	$214.40
7 purchase totals =	$1,202.46		$1,285.2586	$1,285.25	$1,285.25	$1,285.30