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	$236.90	13.613%	$269.1492	$269.15	$269.15	$269.10
Purchase #2	$162.84	10.712%	$180.2834	$180.28	$180.30	$180.30
Purchase #3	$34.87	6.544%	$37.1519	$37.15	$37.15	$37.20
Purchase #4	$133.44	11.324%	$148.5507	$148.55	$148.55	$148.60
Purchase #5	$240.47	3.739%	$249.4612	$249.46	$249.45	$249.50
Purchase #6	$12.49	9.332%	$13.6556	$13.66	$13.65	$13.70
Purchase #7	$102.50	3.214%	$105.7944	$105.79	$105.80	$105.80
7 purchase totals =	$923.51		$1,004.0464	$1,004.04	$1,004.05	$1,004.20