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	$95.91	5.636%	$101.3155	$101.32	$101.30	$101.30
Purchase #2	$81.88	13.112%	$92.6161	$92.62	$92.60	$92.60
Purchase #3	$245.41	12.657%	$276.4715	$276.47	$276.45	$276.50
Purchase #4	$209.28	11.564%	$233.4811	$233.48	$233.50	$233.50
Purchase #5	$90.92	5.430%	$95.857	$95.86	$95.85	$95.90
Purchase #6	$134.30	7.564%	$144.4585	$144.46	$144.45	$144.50
Purchase #7	$247.97	7.377%	$266.2627	$266.26	$266.25	$266.30
7 purchase totals =	$1,105.67		$1,210.4624	$1,210.47	$1,210.40	$1,210.60