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	$91.85	6.567%	$97.8818	$97.88	$97.90	$97.90
Purchase #2	$45.61	10.590%	$50.4401	$50.44	$50.45	$50.40
Purchase #3	$138.68	8.538%	$150.5205	$150.52	$150.50	$150.50
Purchase #4	$19.41	13.340%	$21.9993	$22.00	$22.00	$22.00
Purchase #5	$82.74	4.689%	$86.6197	$86.62	$86.60	$86.60
Purchase #6	$106.44	4.845%	$111.597	$111.60	$111.60	$111.60
Purchase #7	$209.58	11.421%	$233.5161	$233.52	$233.50	$233.50
7 purchase totals =	$694.31		$752.5745	$752.58	$752.55	$752.50