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	5.578%	$175.1539	$175.15	$175.15	$175.20
Purchase #2	$78.25	9.283%	$85.5139	$85.51	$85.50	$85.50
Purchase #3	$36.85	5.312%	$38.8075	$38.81	$38.80	$38.80
Purchase #4	$33.77	3.662%	$35.0067	$35.01	$35.00	$35.00
Purchase #5	$156.84	10.130%	$172.7279	$172.73	$172.75	$172.70
Purchase #6	$94.98	6.674%	$101.319	$101.32	$101.30	$101.30
Purchase #7	$178.27	9.546%	$195.2877	$195.29	$195.30	$195.30
7 purchase totals =	$744.86		$803.8166	$803.82	$803.80	$803.80