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	$40.94	5.340%	$43.1262	$43.13	$43.15	$43.10
Purchase #2	$60.65	11.179%	$67.4301	$67.43	$67.45	$67.40
Purchase #3	$64.75	10.496%	$71.5462	$71.55	$71.55	$71.50
Purchase #4	$192.27	5.397%	$202.6468	$202.65	$202.65	$202.60
Purchase #5	$158.75	4.502%	$165.8969	$165.90	$165.90	$165.90
Purchase #6	$250.43	6.527%	$266.7756	$266.78	$266.80	$266.80
Purchase #7	$50.48	13.765%	$57.4286	$57.43	$57.45	$57.40
7 purchase totals =	$818.27		$874.8504	$874.87	$874.95	$874.70