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	$202.40	5.296%	$213.1191	$213.12	$213.10	$213.10
Purchase #2	$200.34	11.695%	$223.7698	$223.77	$223.75	$223.80
Purchase #3	$179.66	10.721%	$198.9213	$198.92	$198.90	$198.90
Purchase #4	$146.37	8.331%	$158.5641	$158.56	$158.55	$158.60
Purchase #5	$43.85	4.271%	$45.7228	$45.72	$45.70	$45.70
Purchase #6	$19.36	8.233%	$20.9539	$20.95	$20.95	$21.00
Purchase #7	$38.53	5.148%	$40.5135	$40.51	$40.50	$40.50
7 purchase totals =	$830.51		$901.5645	$901.55	$901.45	$901.60