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	$174.96	4.217%	$182.3381	$182.34	$182.35	$182.30
Purchase #2	$171.43	10.185%	$188.8901	$188.89	$188.90	$188.90
Purchase #3	$178.42	7.454%	$191.7194	$191.72	$191.70	$191.70
Purchase #4	$148.59	7.258%	$159.3747	$159.37	$159.35	$159.40
Purchase #5	$87.25	3.570%	$90.3648	$90.36	$90.35	$90.40
Purchase #6	$66.98	6.525%	$71.3504	$71.35	$71.35	$71.40
Purchase #7	$116.38	12.805%	$131.2825	$131.28	$131.30	$131.30
7 purchase totals =	$944.01		$1,015.3200	$1,015.31	$1,015.30	$1,015.40