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	$43.42	3.499%	$44.9393	$44.94	$44.95	$44.90
Purchase #2	$29.72	9.349%	$32.4985	$32.50	$32.50	$32.50
Purchase #3	$249.96	10.275%	$275.6434	$275.64	$275.65	$275.60
Purchase #4	$170.60	8.137%	$184.4817	$184.48	$184.50	$184.50
Purchase #5	$147.29	10.586%	$162.8821	$162.88	$162.90	$162.90
Purchase #6	$50.28	11.767%	$56.1964	$56.20	$56.20	$56.20
Purchase #7	$147.58	12.235%	$165.6364	$165.64	$165.65	$165.60
7 purchase totals =	$838.85		$922.2778	$922.28	$922.35	$922.20