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	$75.72	4.143%	$78.8571	$78.86	$78.85	$78.90
Purchase #2	$227.31	10.164%	$250.4138	$250.41	$250.40	$250.40
Purchase #3	$119.27	5.764%	$126.1447	$126.14	$126.15	$126.10
Purchase #4	$85.38	9.487%	$93.48	$93.48	$93.50	$93.50
Purchase #5	$15.55	11.738%	$17.3753	$17.38	$17.40	$17.40
Purchase #6	$96.64	7.151%	$103.5507	$103.55	$103.55	$103.60
Purchase #7	$32.75	11.437%	$36.4956	$36.50	$36.50	$36.50
7 purchase totals =	$652.62		$706.3172	$706.32	$706.35	$706.40