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	$229.48	13.252%	$259.8907	$259.89	$259.90	$259.90
Purchase #2	$27.91	5.502%	$29.4456	$29.45	$29.45	$29.40
Purchase #3	$135.62	9.739%	$148.828	$148.83	$148.85	$148.80
Purchase #4	$12.77	6.656%	$13.62	$13.62	$13.60	$13.60
Purchase #5	$167.35	9.736%	$183.6432	$183.64	$183.65	$183.60
Purchase #6	$159.66	7.791%	$172.0991	$172.10	$172.10	$172.10
Purchase #7	$174.62	12.580%	$196.5872	$196.59	$196.60	$196.60
7 purchase totals =	$907.41		$1,004.1138	$1,004.12	$1,004.15	$1,004.00