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	$129.70	7.581%	$139.5326	$139.53	$139.55	$139.50
Purchase #2	$176.86	4.714%	$185.1972	$185.20	$185.20	$185.20
Purchase #3	$180.46	4.377%	$188.3587	$188.36	$188.35	$188.40
Purchase #4	$174.30	7.726%	$187.7664	$187.77	$187.75	$187.80
Purchase #5	$171.90	13.632%	$195.3334	$195.33	$195.35	$195.30
Purchase #6	$57.38	9.134%	$62.6211	$62.62	$62.60	$62.60
Purchase #7	$207.33	7.789%	$223.4789	$223.48	$223.50	$223.50
7 purchase totals =	$1,097.93		$1,182.2883	$1,182.29	$1,182.30	$1,182.30