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	$165.90	11.615%	$185.1693	$185.17	$185.15	$185.20
Purchase #2	$34.44	12.507%	$38.7474	$38.75	$38.75	$38.70
Purchase #3	$216.83	6.218%	$230.3125	$230.31	$230.30	$230.30
Purchase #4	$141.27	3.126%	$145.6861	$145.69	$145.70	$145.70
Purchase #5	$103.91	6.209%	$110.3618	$110.36	$110.35	$110.40
Purchase #6	$133.60	13.126%	$151.1363	$151.14	$151.15	$151.10
Purchase #7	$185.69	3.338%	$191.8883	$191.89	$191.90	$191.90
7 purchase totals =	$981.64		$1,053.3017	$1,053.31	$1,053.30	$1,053.30