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	$117.72	5.852%	$124.609	$124.61	$124.60	$124.60
Purchase #2	$145.82	11.682%	$162.8547	$162.85	$162.85	$162.90
Purchase #3	$137.47	10.404%	$151.7724	$151.77	$151.75	$151.80
Purchase #4	$99.40	9.751%	$109.0925	$109.09	$109.10	$109.10
Purchase #5	$196.51	8.234%	$212.6906	$212.69	$212.70	$212.70
Purchase #6	$37.56	6.437%	$39.9777	$39.98	$40.00	$40.00
Purchase #7	$62.29	3.321%	$64.3587	$64.36	$64.35	$64.40
7 purchase totals =	$796.77		$865.3556	$865.35	$865.35	$865.50