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	$88.70	10.531%	$98.041	$98.04	$98.05	$98.00
Purchase #2	$118.57	7.818%	$127.8398	$127.84	$127.85	$127.80
Purchase #3	$160.28	13.770%	$182.3506	$182.35	$182.35	$182.40
Purchase #4	$229.98	10.745%	$254.6914	$254.69	$254.70	$254.70
Purchase #5	$242.39	3.514%	$250.9076	$250.91	$250.90	$250.90
Purchase #6	$108.43	11.493%	$120.8919	$120.89	$120.90	$120.90
Purchase #7	$138.52	6.543%	$147.5834	$147.58	$147.60	$147.60
7 purchase totals =	$1,086.87		$1,182.3057	$1,182.30	$1,182.35	$1,182.30