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	$166.48	5.797%	$176.1308	$176.13	$176.15	$176.10
Purchase #2	$72.77	11.652%	$81.2492	$81.25	$81.25	$81.20
Purchase #3	$40.55	10.385%	$44.7611	$44.76	$44.75	$44.80
Purchase #4	$134.75	5.657%	$142.3728	$142.37	$142.35	$142.40
Purchase #5	$74.68	10.129%	$82.2443	$82.24	$82.25	$82.20
Purchase #6	$59.29	8.111%	$64.099	$64.10	$64.10	$64.10
Purchase #7	$55.79	6.566%	$59.4532	$59.45	$59.45	$59.50
7 purchase totals =	$604.31		$650.3104	$650.30	$650.30	$650.30