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	$238.93	9.131%	$260.7467	$260.75	$260.75	$260.70
Purchase #2	$219.69	7.541%	$236.2568	$236.26	$236.25	$236.30
Purchase #3	$164.41	11.618%	$183.5112	$183.51	$183.50	$183.50
Purchase #4	$46.89	13.128%	$53.0457	$53.05	$53.05	$53.00
Purchase #5	$146.36	9.233%	$159.8734	$159.87	$159.85	$159.90
Purchase #6	$86.51	3.282%	$89.3493	$89.35	$89.35	$89.30
Purchase #7	$198.75	7.431%	$213.5191	$213.52	$213.50	$213.50
7 purchase totals =	$1,101.54		$1,196.3022	$1,196.31	$1,196.25	$1,196.20