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	$137.53	4.168%	$143.2623	$143.26	$143.25	$143.30
Purchase #2	$189.62	13.687%	$215.5733	$215.57	$215.55	$215.60
Purchase #3	$66.59	7.689%	$71.7101	$71.71	$71.70	$71.70
Purchase #4	$152.89	3.436%	$158.1433	$158.14	$158.15	$158.10
Purchase #5	$33.30	5.797%	$35.2304	$35.23	$35.25	$35.20
Purchase #6	$136.34	4.726%	$142.7834	$142.78	$142.80	$142.80
Purchase #7	$244.50	3.533%	$253.1382	$253.14	$253.15	$253.10
7 purchase totals =	$960.77		$1,019.8410	$1,019.83	$1,019.85	$1,019.80