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	$97.84	8.456%	$106.1134	$106.11	$106.10	$106.10
Purchase #2	$230.25	5.550%	$243.0289	$243.03	$243.05	$243.00
Purchase #3	$82.67	7.760%	$89.0852	$89.09	$89.10	$89.10
Purchase #4	$25.85	11.443%	$28.808	$28.81	$28.80	$28.80
Purchase #5	$91.78	10.559%	$101.4711	$101.47	$101.45	$101.50
Purchase #6	$106.86	13.678%	$121.4763	$121.48	$121.50	$121.50
Purchase #7	$182.88	7.417%	$196.4442	$196.44	$196.45	$196.40
7 purchase totals =	$818.13		$886.4271	$886.43	$886.45	$886.40