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	$227.27	10.113%	$250.2538	$250.25	$250.25	$250.30
Purchase #2	$83.59	9.539%	$91.5637	$91.56	$91.55	$91.60
Purchase #3	$19.57	6.718%	$20.8847	$20.88	$20.90	$20.90
Purchase #4	$168.25	13.250%	$190.5431	$190.54	$190.55	$190.50
Purchase #5	$210.42	10.375%	$232.2511	$232.25	$232.25	$232.30
Purchase #6	$177.45	8.265%	$192.1162	$192.12	$192.10	$192.10
Purchase #7	$229.31	7.373%	$246.217	$246.22	$246.20	$246.20
7 purchase totals =	$1,115.86		$1,223.8296	$1,223.82	$1,223.80	$1,223.90