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	$22.99	10.175%	$25.3292	$25.33	$25.35	$25.30
Purchase #2	$180.42	10.269%	$198.9473	$198.95	$198.95	$198.90
Purchase #3	$137.60	6.710%	$146.833	$146.83	$146.85	$146.80
Purchase #4	$42.88	6.681%	$45.7448	$45.74	$45.75	$45.70
Purchase #5	$84.72	8.172%	$91.6433	$91.64	$91.65	$91.60
Purchase #6	$25.27	13.143%	$28.5912	$28.59	$28.60	$28.60
Purchase #7	$249.57	6.366%	$265.4576	$265.46	$265.45	$265.50
7 purchase totals =	$743.45		$802.5464	$802.54	$802.60	$802.40