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	$215.57	12.849%	$243.2686	$243.27	$243.25	$243.30
Purchase #2	$10.61	12.664%	$11.9537	$11.95	$11.95	$12.00
Purchase #3	$136.45	11.485%	$152.1213	$152.12	$152.10	$152.10
Purchase #4	$156.26	11.502%	$174.233	$174.23	$174.25	$174.20
Purchase #5	$232.61	12.826%	$262.4446	$262.44	$262.45	$262.40
Purchase #6	$215.71	12.330%	$242.307	$242.31	$242.30	$242.30
Purchase #7	$116.91	8.812%	$127.2121	$127.21	$127.20	$127.20
7 purchase totals =	$1,084.12		$1,213.5403	$1,213.53	$1,213.50	$1,213.50