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	$191.71	6.719%	$204.591	$204.59	$204.60	$204.60
Purchase #2	$227.46	5.587%	$240.1682	$240.17	$240.15	$240.20
Purchase #3	$54.72	13.467%	$62.0891	$62.09	$62.10	$62.10
Purchase #4	$25.70	4.502%	$26.857	$26.86	$26.85	$26.90
Purchase #5	$225.36	13.323%	$255.3847	$255.38	$255.40	$255.40
Purchase #6	$71.73	10.750%	$79.441	$79.44	$79.45	$79.40
Purchase #7	$200.78	5.543%	$211.9092	$211.91	$211.90	$211.90
7 purchase totals =	$997.46		$1,080.4402	$1,080.44	$1,080.45	$1,080.50