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	$129.33	12.447%	$145.4277	$145.43	$145.45	$145.40
Purchase #2	$237.26	7.717%	$255.5694	$255.57	$255.55	$255.60
Purchase #3	$170.33	12.393%	$191.439	$191.44	$191.45	$191.40
Purchase #4	$171.87	11.648%	$191.8894	$191.89	$191.90	$191.90
Purchase #5	$247.74	10.709%	$274.2705	$274.27	$274.25	$274.30
Purchase #6	$62.99	8.818%	$68.5445	$68.54	$68.55	$68.50
Purchase #7	$54.56	9.829%	$59.9227	$59.92	$59.90	$59.90
7 purchase totals =	$1,074.08		$1,187.0632	$1,187.06	$1,187.05	$1,187.00