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	$159.34	8.205%	$172.4138	$172.41	$172.40	$172.40
Purchase #2	$215.86	4.475%	$225.5197	$225.52	$225.50	$225.50
Purchase #3	$70.29	8.499%	$76.2639	$76.26	$76.25	$76.30
Purchase #4	$119.93	10.455%	$132.4687	$132.47	$132.45	$132.50
Purchase #5	$7.74	9.135%	$8.447	$8.45	$8.45	$8.40
Purchase #6	$115.87	7.461%	$124.5151	$124.52	$124.50	$124.50
Purchase #7	$40.52	4.385%	$42.2968	$42.30	$42.30	$42.30
7 purchase totals =	$729.55		$781.9250	$781.93	$781.85	$781.90