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	$106.41	10.546%	$117.632	$117.63	$117.65	$117.60
Purchase #2	$99.95	3.442%	$103.3903	$103.39	$103.40	$103.40
Purchase #3	$238.37	4.223%	$248.4364	$248.44	$248.45	$248.40
Purchase #4	$151.52	4.572%	$158.4475	$158.45	$158.45	$158.40
Purchase #5	$72.25	7.609%	$77.7475	$77.75	$77.75	$77.70
Purchase #6	$118.34	11.268%	$131.6746	$131.67	$131.65	$131.70
Purchase #7	$191.26	13.404%	$216.8965	$216.90	$216.90	$216.90
7 purchase totals =	$978.10		$1,054.2248	$1,054.23	$1,054.25	$1,054.10