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	$133.60	11.332%	$148.7396	$148.74	$148.75	$148.70
Purchase #2	$133.61	12.198%	$149.9077	$149.91	$149.90	$149.90
Purchase #3	$95.87	3.527%	$99.2513	$99.25	$99.25	$99.30
Purchase #4	$182.31	12.752%	$205.5582	$205.56	$205.55	$205.60
Purchase #5	$90.94	6.181%	$96.561	$96.56	$96.55	$96.60
Purchase #6	$180.91	5.187%	$190.2938	$190.29	$190.30	$190.30
Purchase #7	$160.87	11.796%	$179.8462	$179.85	$179.85	$179.80
7 purchase totals =	$978.11		$1,070.1578	$1,070.16	$1,070.15	$1,070.20