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	$79.33	4.785%	$83.1259	$83.13	$83.15	$83.10
Purchase #2	$54.46	10.303%	$60.071	$60.07	$60.05	$60.10
Purchase #3	$109.90	6.872%	$117.4523	$117.45	$117.45	$117.50
Purchase #4	$5.64	6.401%	$6.001	$6.00	$6.00	$6.00
Purchase #5	$127.30	13.524%	$144.5161	$144.52	$144.50	$144.50
Purchase #6	$114.41	5.205%	$120.365	$120.37	$120.35	$120.40
Purchase #7	$32.28	4.817%	$33.8349	$33.83	$33.85	$33.80
7 purchase totals =	$523.32		$565.3662	$565.37	$565.35	$565.40