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	$171.84	7.729%	$185.1215	$185.12	$185.10	$185.10
Purchase #2	$164.56	4.618%	$172.1594	$172.16	$172.15	$172.20
Purchase #3	$177.70	3.858%	$184.5557	$184.56	$184.55	$184.60
Purchase #4	$213.78	13.865%	$243.4206	$243.42	$243.40	$243.40
Purchase #5	$11.56	9.270%	$12.6316	$12.63	$12.65	$12.60
Purchase #6	$34.70	9.830%	$38.111	$38.11	$38.10	$38.10
Purchase #7	$167.83	5.137%	$176.4514	$176.45	$176.45	$176.50
7 purchase totals =	$941.97		$1,012.4512	$1,012.45	$1,012.40	$1,012.50