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	$196.66	6.536%	$209.5137	$209.51	$209.50	$209.50
Purchase #2	$51.38	7.327%	$55.1446	$55.14	$55.15	$55.10
Purchase #3	$67.83	8.726%	$73.7488	$73.75	$73.75	$73.70
Purchase #4	$26.64	5.355%	$28.0666	$28.07	$28.05	$28.10
Purchase #5	$146.50	4.402%	$152.9489	$152.95	$152.95	$152.90
Purchase #6	$62.40	5.544%	$65.8595	$65.86	$65.85	$65.90
Purchase #7	$155.85	10.293%	$171.8916	$171.89	$171.90	$171.90
7 purchase totals =	$707.26		$757.1737	$757.17	$757.15	$757.10