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	$161.42	4.211%	$168.2174	$168.22	$168.20	$168.20
Purchase #2	$218.98	4.175%	$228.1224	$228.12	$228.10	$228.10
Purchase #3	$34.39	11.304%	$38.2774	$38.28	$38.30	$38.30
Purchase #4	$35.60	13.543%	$40.4213	$40.42	$40.40	$40.40
Purchase #5	$85.97	5.721%	$90.8883	$90.89	$90.90	$90.90
Purchase #6	$88.56	10.134%	$97.5347	$97.53	$97.55	$97.50
Purchase #7	$175.94	7.505%	$189.1443	$189.14	$189.15	$189.10
7 purchase totals =	$800.86		$852.6058	$852.60	$852.60	$852.50