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	$143.97	11.165%	$160.0443	$160.04	$160.05	$160.00
Purchase #2	$142.73	6.616%	$152.173	$152.17	$152.15	$152.20
Purchase #3	$147.27	4.674%	$154.1534	$154.15	$154.15	$154.20
Purchase #4	$37.91	12.666%	$42.7117	$42.71	$42.70	$42.70
Purchase #5	$24.29	4.300%	$25.3345	$25.33	$25.35	$25.30
Purchase #6	$155.49	10.229%	$171.3951	$171.40	$171.40	$171.40
Purchase #7	$151.85	3.330%	$156.9066	$156.91	$156.90	$156.90
7 purchase totals =	$803.51		$862.7186	$862.71	$862.70	$862.70