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	$69.86	3.141%	$72.0543	$72.05	$72.05	$72.10
Purchase #2	$209.42	6.872%	$223.8113	$223.81	$223.80	$223.80
Purchase #3	$142.55	6.585%	$151.9369	$151.94	$151.95	$151.90
Purchase #4	$144.74	5.647%	$152.9135	$152.91	$152.90	$152.90
Purchase #5	$182.66	13.364%	$207.0707	$207.07	$207.05	$207.10
Purchase #6	$76.35	12.408%	$85.8235	$85.82	$85.80	$85.80
Purchase #7	$165.85	8.361%	$179.7167	$179.72	$179.70	$179.70
7 purchase totals =	$991.43		$1,073.3269	$1,073.32	$1,073.25	$1,073.30