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	$187.28	11.478%	$208.776	$208.78	$208.80	$208.80
Purchase #2	$112.87	6.784%	$120.5271	$120.53	$120.55	$120.50
Purchase #3	$50.30	8.114%	$54.3813	$54.38	$54.40	$54.40
Purchase #4	$229.86	10.700%	$254.455	$254.46	$254.45	$254.50
Purchase #5	$220.55	5.782%	$233.3022	$233.30	$233.30	$233.30
Purchase #6	$133.37	9.867%	$146.5296	$146.53	$146.55	$146.50
Purchase #7	$113.74	9.569%	$124.6238	$124.62	$124.60	$124.60
7 purchase totals =	$1,047.97		$1,142.5950	$1,142.60	$1,142.65	$1,142.60