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	$56.64	10.288%	$62.4671	$62.47	$62.45	$62.50
Purchase #2	$165.49	4.474%	$172.894	$172.89	$172.90	$172.90
Purchase #3	$108.42	10.674%	$119.9928	$119.99	$120.00	$120.00
Purchase #4	$35.41	7.642%	$38.116	$38.12	$38.10	$38.10
Purchase #5	$127.39	5.630%	$134.5621	$134.56	$134.55	$134.60
Purchase #6	$222.36	12.827%	$250.8821	$250.88	$250.90	$250.90
Purchase #7	$108.48	4.407%	$113.2607	$113.26	$113.25	$113.30
7 purchase totals =	$824.19		$892.1748	$892.17	$892.15	$892.30