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	$105.89	5.669%	$111.8929	$111.89	$111.90	$111.90
Purchase #2	$92.80	11.586%	$103.5518	$103.55	$103.55	$103.60
Purchase #3	$82.57	11.251%	$91.86	$91.86	$91.85	$91.90
Purchase #4	$152.47	7.854%	$164.445	$164.45	$164.45	$164.40
Purchase #5	$120.50	8.873%	$131.192	$131.19	$131.20	$131.20
Purchase #6	$116.61	6.528%	$124.2223	$124.22	$124.20	$124.20
Purchase #7	$18.59	13.840%	$21.1629	$21.16	$21.15	$21.20
7 purchase totals =	$689.43		$748.3269	$748.32	$748.30	$748.40