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	$140.96	11.711%	$157.4678	$157.47	$157.45	$157.50
Purchase #2	$157.83	5.164%	$165.9803	$165.98	$166.00	$166.00
Purchase #3	$40.50	10.673%	$44.8226	$44.82	$44.80	$44.80
Purchase #4	$61.27	6.368%	$65.1717	$65.17	$65.15	$65.20
Purchase #5	$114.98	11.182%	$127.8371	$127.84	$127.85	$127.80
Purchase #6	$231.54	9.451%	$253.4228	$253.42	$253.40	$253.40
Purchase #7	$222.46	6.352%	$236.5907	$236.59	$236.60	$236.60
7 purchase totals =	$969.54		$1,051.2930	$1,051.29	$1,051.25	$1,051.30