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	$23.82	6.766%	$25.4317	$25.43	$25.45	$25.40
Purchase #2	$154.71	11.191%	$172.0236	$172.02	$172.00	$172.00
Purchase #3	$246.41	11.822%	$275.5406	$275.54	$275.55	$275.50
Purchase #4	$168.89	5.385%	$177.9847	$177.98	$178.00	$178.00
Purchase #5	$161.86	8.662%	$175.8803	$175.88	$175.90	$175.90
Purchase #6	$96.78	10.727%	$107.1616	$107.16	$107.15	$107.20
Purchase #7	$74.63	10.428%	$82.4124	$82.41	$82.40	$82.40
7 purchase totals =	$927.10		$1,016.4349	$1,016.42	$1,016.45	$1,016.40