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	$191.68	10.317%	$211.4556	$211.46	$211.45	$211.50
Purchase #2	$207.26	4.470%	$216.5245	$216.52	$216.50	$216.50
Purchase #3	$148.56	4.648%	$155.4651	$155.47	$155.45	$155.50
Purchase #4	$47.38	9.526%	$51.8934	$51.89	$51.90	$51.90
Purchase #5	$239.52	8.337%	$259.4888	$259.49	$259.50	$259.50
Purchase #6	$159.34	7.749%	$171.6873	$171.69	$171.70	$171.70
Purchase #7	$147.80	11.742%	$165.1547	$165.15	$165.15	$165.20
7 purchase totals =	$1,141.54		$1,231.6694	$1,231.67	$1,231.65	$1,231.80