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	$242.76	9.751%	$266.4315	$266.43	$266.45	$266.40
Purchase #2	$205.82	8.423%	$223.1562	$223.16	$223.15	$223.20
Purchase #3	$185.46	6.287%	$197.1199	$197.12	$197.10	$197.10
Purchase #4	$44.87	11.815%	$50.1714	$50.17	$50.15	$50.20
Purchase #5	$41.85	10.760%	$46.3531	$46.35	$46.35	$46.40
Purchase #6	$196.58	13.632%	$223.3778	$223.38	$223.40	$223.40
Purchase #7	$55.69	11.719%	$62.2163	$62.22	$62.20	$62.20
7 purchase totals =	$973.03		$1,068.8262	$1,068.83	$1,068.80	$1,068.90