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	$161.71	6.258%	$171.8298	$171.83	$171.85	$171.80
Purchase #2	$88.35	7.674%	$95.13	$95.13	$95.15	$95.10
Purchase #3	$54.69	5.730%	$57.8237	$57.82	$57.80	$57.80
Purchase #4	$244.70	4.872%	$256.6218	$256.62	$256.60	$256.60
Purchase #5	$105.74	8.179%	$114.3885	$114.39	$114.40	$114.40
Purchase #6	$189.28	10.312%	$208.7986	$208.80	$208.80	$208.80
Purchase #7	$131.65	8.494%	$142.8324	$142.83	$142.85	$142.80
7 purchase totals =	$976.12		$1,047.4248	$1,047.42	$1,047.45	$1,047.30