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	$200.57	12.295%	$225.2301	$225.23	$225.25	$225.20
Purchase #2	$49.60	11.634%	$55.3705	$55.37	$55.35	$55.40
Purchase #3	$79.90	12.228%	$89.6702	$89.67	$89.65	$89.70
Purchase #4	$160.48	7.296%	$172.1886	$172.19	$172.20	$172.20
Purchase #5	$190.47	9.170%	$207.9361	$207.94	$207.95	$207.90
Purchase #6	$209.89	5.841%	$222.1497	$222.15	$222.15	$222.10
Purchase #7	$203.42	11.792%	$227.4073	$227.41	$227.40	$227.40
7 purchase totals =	$1,094.33		$1,199.9525	$1,199.96	$1,199.95	$1,199.90