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	$183.25	6.139%	$194.4997	$194.50	$194.50	$194.50
Purchase #2	$42.43	6.654%	$45.2533	$45.25	$45.25	$45.30
Purchase #3	$40.38	6.665%	$43.0713	$43.07	$43.05	$43.10
Purchase #4	$211.32	7.485%	$227.1373	$227.14	$227.15	$227.10
Purchase #5	$173.37	3.468%	$179.3825	$179.38	$179.40	$179.40
Purchase #6	$39.64	4.354%	$41.3659	$41.37	$41.35	$41.40
Purchase #7	$83.93	7.205%	$89.9772	$89.98	$90.00	$90.00
7 purchase totals =	$774.32		$820.6872	$820.69	$820.70	$820.80