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	$236.99	6.761%	$253.0129	$253.01	$253.00	$253.00
Purchase #2	$26.80	11.655%	$29.9235	$29.92	$29.90	$29.90
Purchase #3	$60.77	11.726%	$67.8959	$67.90	$67.90	$67.90
Purchase #4	$92.51	13.624%	$105.1136	$105.11	$105.10	$105.10
Purchase #5	$241.87	11.328%	$269.269	$269.27	$269.25	$269.30
Purchase #6	$174.31	12.849%	$196.7071	$196.71	$196.70	$196.70
Purchase #7	$128.47	9.665%	$140.8866	$140.89	$140.90	$140.90
7 purchase totals =	$961.72		$1,062.8086	$1,062.81	$1,062.75	$1,062.80