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	$117.73	11.418%	$131.1724	$131.17	$131.15	$131.20
Purchase #2	$136.42	7.143%	$146.1645	$146.16	$146.15	$146.20
Purchase #3	$175.76	11.762%	$196.4329	$196.43	$196.45	$196.40
Purchase #4	$196.99	12.221%	$221.0641	$221.06	$221.05	$221.10
Purchase #5	$228.38	8.604%	$248.0298	$248.03	$248.05	$248.00
Purchase #6	$48.33	13.464%	$54.8372	$54.84	$54.85	$54.80
Purchase #7	$131.35	11.527%	$146.4907	$146.49	$146.50	$146.50
7 purchase totals =	$1,034.96		$1,144.1916	$1,144.18	$1,144.20	$1,144.20