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	$142.78	13.567%	$162.151	$162.15	$162.15	$162.20
Purchase #2	$172.43	3.831%	$179.0358	$179.04	$179.05	$179.00
Purchase #3	$136.29	3.709%	$141.345	$141.35	$141.35	$141.30
Purchase #4	$222.57	3.345%	$230.015	$230.02	$230.00	$230.00
Purchase #5	$48.54	8.644%	$52.7358	$52.74	$52.75	$52.70
Purchase #6	$223.44	5.388%	$235.4789	$235.48	$235.50	$235.50
Purchase #7	$89.85	7.198%	$96.3174	$96.32	$96.30	$96.30
7 purchase totals =	$1,035.90		$1,097.0789	$1,097.10	$1,097.10	$1,097.00