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	$50.64	5.430%	$53.3898	$53.39	$53.40	$53.40
Purchase #2	$138.31	9.775%	$151.8298	$151.83	$151.85	$151.80
Purchase #3	$72.58	6.774%	$77.4966	$77.50	$77.50	$77.50
Purchase #4	$65.56	10.521%	$72.4576	$72.46	$72.45	$72.50
Purchase #5	$191.43	7.464%	$205.7183	$205.72	$205.70	$205.70
Purchase #6	$114.39	4.208%	$119.2035	$119.20	$119.20	$119.20
Purchase #7	$51.31	4.744%	$53.7441	$53.74	$53.75	$53.70
7 purchase totals =	$684.22		$733.8397	$733.84	$733.85	$733.80