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	$185.39	3.473%	$191.8286	$191.83	$191.85	$191.80
Purchase #2	$124.72	13.540%	$141.6071	$141.61	$141.60	$141.60
Purchase #3	$186.33	11.441%	$207.648	$207.65	$207.65	$207.60
Purchase #4	$127.64	11.603%	$142.4501	$142.45	$142.45	$142.50
Purchase #5	$48.35	3.645%	$50.1124	$50.11	$50.10	$50.10
Purchase #6	$190.54	6.840%	$203.5729	$203.57	$203.55	$203.60
Purchase #7	$172.49	5.709%	$182.3375	$182.34	$182.35	$182.30
7 purchase totals =	$1,035.46		$1,119.5566	$1,119.56	$1,119.55	$1,119.50