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	$101.65	12.851%	$114.713	$114.71	$114.70	$114.70
Purchase #2	$245.78	12.227%	$275.8315	$275.83	$275.85	$275.80
Purchase #3	$10.89	12.688%	$12.2717	$12.27	$12.25	$12.30
Purchase #4	$245.91	7.702%	$264.85	$264.85	$264.85	$264.90
Purchase #5	$88.41	6.489%	$94.1469	$94.15	$94.15	$94.10
Purchase #6	$161.77	11.788%	$180.8394	$180.84	$180.85	$180.80
Purchase #7	$186.61	10.862%	$206.8796	$206.88	$206.90	$206.90
7 purchase totals =	$1,041.02		$1,149.5321	$1,149.53	$1,149.55	$1,149.50