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	$74.67	3.697%	$77.4305	$77.43	$77.45	$77.40
Purchase #2	$162.70	13.154%	$184.1016	$184.10	$184.10	$184.10
Purchase #3	$246.84	11.557%	$275.3673	$275.37	$275.35	$275.40
Purchase #4	$51.77	7.580%	$55.6942	$55.69	$55.70	$55.70
Purchase #5	$200.85	9.688%	$220.3083	$220.31	$220.30	$220.30
Purchase #6	$146.36	4.251%	$152.5818	$152.58	$152.60	$152.60
Purchase #7	$156.69	6.772%	$167.301	$167.30	$167.30	$167.30
7 purchase totals =	$1,039.88		$1,132.7847	$1,132.78	$1,132.80	$1,132.80