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	$223.87	5.194%	$235.4978	$235.50	$235.50	$235.50
Purchase #2	$87.28	5.854%	$92.3894	$92.39	$92.40	$92.40
Purchase #3	$230.92	6.104%	$245.0154	$245.02	$245.00	$245.00
Purchase #4	$156.42	9.465%	$171.2252	$171.23	$171.25	$171.20
Purchase #5	$93.56	12.342%	$105.1072	$105.11	$105.10	$105.10
Purchase #6	$124.43	3.854%	$129.2255	$129.23	$129.25	$129.20
Purchase #7	$152.28	13.104%	$172.2348	$172.23	$172.25	$172.20
7 purchase totals =	$1,068.76		$1,150.6953	$1,150.71	$1,150.75	$1,150.60