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	$68.59	6.279%	$72.8968	$72.90	$72.90	$72.90
Purchase #2	$90.57	6.224%	$96.2071	$96.21	$96.20	$96.20
Purchase #3	$112.30	13.239%	$127.1674	$127.17	$127.15	$127.20
Purchase #4	$115.86	7.104%	$124.0907	$124.09	$124.10	$124.10
Purchase #5	$160.48	6.321%	$170.6239	$170.62	$170.60	$170.60
Purchase #6	$92.89	11.662%	$103.7228	$103.72	$103.70	$103.70
Purchase #7	$45.53	6.204%	$48.3547	$48.35	$48.35	$48.40
7 purchase totals =	$686.22		$743.0634	$743.06	$743.00	$743.10