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	$234.50	12.385%	$263.5428	$263.54	$263.55	$263.50
Purchase #2	$235.83	7.119%	$252.6187	$252.62	$252.60	$252.60
Purchase #3	$91.40	8.456%	$99.1288	$99.13	$99.15	$99.10
Purchase #4	$78.98	13.847%	$89.9164	$89.92	$89.90	$89.90
Purchase #5	$27.26	13.544%	$30.9521	$30.95	$30.95	$31.00
Purchase #6	$171.95	5.583%	$181.55	$181.55	$181.55	$181.60
Purchase #7	$167.39	11.554%	$186.7302	$186.73	$186.75	$186.70
7 purchase totals =	$1,007.31		$1,104.4390	$1,104.44	$1,104.45	$1,104.40