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	$49.27	11.640%	$55.005	$55.01	$55.00	$55.00
Purchase #2	$151.42	13.490%	$171.8466	$171.85	$171.85	$171.80
Purchase #3	$55.94	6.756%	$59.7193	$59.72	$59.70	$59.70
Purchase #4	$33.83	9.855%	$37.1639	$37.16	$37.15	$37.20
Purchase #5	$184.34	11.855%	$206.1935	$206.19	$206.20	$206.20
Purchase #6	$188.55	13.710%	$214.4002	$214.40	$214.40	$214.40
Purchase #7	$235.91	12.537%	$265.486	$265.49	$265.50	$265.50
7 purchase totals =	$899.26		$1,009.8145	$1,009.82	$1,009.80	$1,009.80