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	$199.94	5.272%	$210.4808	$210.48	$210.50	$210.50
Purchase #2	$39.48	6.792%	$42.1615	$42.16	$42.15	$42.20
Purchase #3	$240.70	10.112%	$265.0396	$265.04	$265.05	$265.00
Purchase #4	$156.70	5.863%	$165.8873	$165.89	$165.90	$165.90
Purchase #5	$211.66	5.523%	$223.35	$223.35	$223.35	$223.40
Purchase #6	$146.95	13.642%	$166.9969	$167.00	$167.00	$167.00
Purchase #7	$120.82	5.257%	$127.1715	$127.17	$127.15	$127.20
7 purchase totals =	$1,116.25		$1,201.0876	$1,201.09	$1,201.10	$1,201.20