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	$70.47	9.617%	$77.2471	$77.25	$77.25	$77.20
Purchase #2	$166.46	12.459%	$187.1993	$187.20	$187.20	$187.20
Purchase #3	$94.41	9.702%	$103.5697	$103.57	$103.55	$103.60
Purchase #4	$244.95	4.702%	$256.4675	$256.47	$256.45	$256.50
Purchase #5	$146.84	4.794%	$153.8795	$153.88	$153.90	$153.90
Purchase #6	$219.50	11.306%	$244.3167	$244.32	$244.30	$244.30
Purchase #7	$61.87	10.788%	$68.5445	$68.54	$68.55	$68.50
7 purchase totals =	$1,004.50		$1,091.2243	$1,091.23	$1,091.20	$1,091.20