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	$146.52	5.331%	$154.331	$154.33	$154.35	$154.30
Purchase #2	$50.79	7.677%	$54.6891	$54.69	$54.70	$54.70
Purchase #3	$43.72	7.790%	$47.1258	$47.13	$47.15	$47.10
Purchase #4	$56.59	10.367%	$62.4567	$62.46	$62.45	$62.50
Purchase #5	$91.40	11.731%	$102.1221	$102.12	$102.10	$102.10
Purchase #6	$74.44	7.496%	$80.02	$80.02	$80.00	$80.00
Purchase #7	$71.70	9.602%	$78.5846	$78.58	$78.60	$78.60
7 purchase totals =	$535.16		$579.3293	$579.33	$579.35	$579.30