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	$100.88	10.804%	$111.7791	$111.78	$111.80	$111.80
Purchase #2	$114.48	5.362%	$120.6184	$120.62	$120.60	$120.60
Purchase #3	$199.90	6.397%	$212.6876	$212.69	$212.70	$212.70
Purchase #4	$208.86	5.125%	$219.5641	$219.56	$219.55	$219.60
Purchase #5	$18.32	6.147%	$19.4461	$19.45	$19.45	$19.40
Purchase #6	$85.99	4.503%	$89.8621	$89.86	$89.85	$89.90
Purchase #7	$11.61	4.731%	$12.1593	$12.16	$12.15	$12.20
7 purchase totals =	$740.04		$786.1167	$786.12	$786.10	$786.20