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	$178.40	7.393%	$191.5891	$191.59	$191.60	$191.60
Purchase #2	$11.36	9.578%	$12.4481	$12.45	$12.45	$12.40
Purchase #3	$47.54	13.764%	$54.0834	$54.08	$54.10	$54.10
Purchase #4	$77.47	13.378%	$87.8339	$87.83	$87.85	$87.80
Purchase #5	$147.87	10.198%	$162.9498	$162.95	$162.95	$162.90
Purchase #6	$246.52	3.433%	$254.983	$254.98	$255.00	$255.00
Purchase #7	$248.30	11.123%	$275.9184	$275.92	$275.90	$275.90
7 purchase totals =	$957.46		$1,039.8057	$1,039.80	$1,039.85	$1,039.70