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	$163.25	5.361%	$172.0018	$172.00	$172.00	$172.00
Purchase #2	$116.59	12.702%	$131.3993	$131.40	$131.40	$131.40
Purchase #3	$24.72	10.782%	$27.3853	$27.39	$27.40	$27.40
Purchase #4	$222.49	12.411%	$250.1032	$250.10	$250.10	$250.10
Purchase #5	$37.77	8.216%	$40.8732	$40.87	$40.85	$40.90
Purchase #6	$48.30	8.299%	$52.3084	$52.31	$52.30	$52.30
Purchase #7	$53.53	6.852%	$57.1979	$57.20	$57.20	$57.20
7 purchase totals =	$666.65		$731.2691	$731.27	$731.25	$731.30