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	$235.58	11.698%	$263.1381	$263.14	$263.15	$263.10
Purchase #2	$92.50	11.460%	$103.1005	$103.10	$103.10	$103.10
Purchase #3	$85.48	3.431%	$88.4128	$88.41	$88.40	$88.40
Purchase #4	$103.66	12.520%	$116.6382	$116.64	$116.65	$116.60
Purchase #5	$191.72	4.751%	$200.8286	$200.83	$200.85	$200.80
Purchase #6	$85.90	7.780%	$92.583	$92.58	$92.60	$92.60
Purchase #7	$126.90	7.727%	$136.7056	$136.71	$136.70	$136.70
7 purchase totals =	$921.74		$1,001.4068	$1,001.41	$1,001.45	$1,001.30