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	$155.83	10.381%	$172.0067	$172.01	$172.00	$172.00
Purchase #2	$6.66	8.373%	$7.2176	$7.22	$7.20	$7.20
Purchase #3	$175.50	3.800%	$182.169	$182.17	$182.15	$182.20
Purchase #4	$46.76	11.819%	$52.2866	$52.29	$52.30	$52.30
Purchase #5	$104.57	6.829%	$111.7111	$111.71	$111.70	$111.70
Purchase #6	$91.39	8.511%	$99.1682	$99.17	$99.15	$99.20
Purchase #7	$101.43	6.744%	$108.2704	$108.27	$108.25	$108.30
7 purchase totals =	$682.14		$732.8296	$732.84	$732.75	$732.90