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	$197.41	4.502%	$206.2974	$206.30	$206.30	$206.30
Purchase #2	$139.69	10.455%	$154.2946	$154.29	$154.30	$154.30
Purchase #3	$123.28	3.402%	$127.474	$127.47	$127.45	$127.50
Purchase #4	$173.33	12.681%	$195.31	$195.31	$195.30	$195.30
Purchase #5	$192.26	7.585%	$206.8429	$206.84	$206.85	$206.80
Purchase #6	$216.25	3.158%	$223.0792	$223.08	$223.10	$223.10
Purchase #7	$17.67	4.286%	$18.4273	$18.43	$18.45	$18.40
7 purchase totals =	$1,059.89		$1,131.7254	$1,131.72	$1,131.75	$1,131.70