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	$88.34	3.303%	$91.2579	$91.26	$91.25	$91.30
Purchase #2	$46.87	7.430%	$50.3524	$50.35	$50.35	$50.40
Purchase #3	$156.80	10.104%	$172.6431	$172.64	$172.65	$172.60
Purchase #4	$174.31	10.415%	$192.4644	$192.46	$192.45	$192.50
Purchase #5	$89.66	3.182%	$92.513	$92.51	$92.50	$92.50
Purchase #6	$7.80	13.434%	$8.8479	$8.85	$8.85	$8.80
Purchase #7	$233.56	12.322%	$262.3393	$262.34	$262.35	$262.30
7 purchase totals =	$797.34		$870.4180	$870.41	$870.40	$870.40