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	$141.56	11.739%	$158.1777	$158.18	$158.20	$158.20
Purchase #2	$89.41	3.451%	$92.4955	$92.50	$92.50	$92.50
Purchase #3	$98.27	3.282%	$101.4952	$101.50	$101.50	$101.50
Purchase #4	$216.90	10.370%	$239.3925	$239.39	$239.40	$239.40
Purchase #5	$68.77	9.822%	$75.5246	$75.52	$75.50	$75.50
Purchase #6	$31.51	4.598%	$32.9588	$32.96	$32.95	$33.00
Purchase #7	$233.40	9.498%	$255.5683	$255.57	$255.55	$255.60
7 purchase totals =	$879.82		$955.6126	$955.62	$955.60	$955.70