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	$107.55	9.418%	$117.6791	$117.68	$117.70	$117.70
Purchase #2	$64.58	11.319%	$71.8898	$71.89	$71.90	$71.90
Purchase #3	$51.82	6.144%	$55.0038	$55.00	$55.00	$55.00
Purchase #4	$247.96	8.630%	$269.3589	$269.36	$269.35	$269.40
Purchase #5	$48.89	12.300%	$54.9035	$54.90	$54.90	$54.90
Purchase #6	$152.77	13.713%	$173.7194	$173.72	$173.70	$173.70
Purchase #7	$83.62	11.586%	$93.3082	$93.31	$93.30	$93.30
7 purchase totals =	$757.19		$835.8627	$835.86	$835.85	$835.90