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	$92.28	4.660%	$96.5802	$96.58	$96.60	$96.60
Purchase #2	$233.84	4.275%	$243.8367	$243.84	$243.85	$243.80
Purchase #3	$19.89	4.217%	$20.7288	$20.73	$20.75	$20.70
Purchase #4	$84.31	13.497%	$95.6893	$95.69	$95.70	$95.70
Purchase #5	$91.41	9.754%	$100.3261	$100.33	$100.35	$100.30
Purchase #6	$66.70	10.674%	$73.8196	$73.82	$73.80	$73.80
Purchase #7	$59.35	5.671%	$62.7157	$62.72	$62.70	$62.70
7 purchase totals =	$647.78		$693.6964	$693.71	$693.75	$693.60