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	$149.38	10.710%	$165.3786	$165.38	$165.40	$165.40
Purchase #2	$161.31	8.779%	$175.4714	$175.47	$175.45	$175.50
Purchase #3	$92.78	9.531%	$101.6229	$101.62	$101.60	$101.60
Purchase #4	$173.90	3.830%	$180.5604	$180.56	$180.55	$180.60
Purchase #5	$146.67	3.280%	$151.4808	$151.48	$151.50	$151.50
Purchase #6	$206.95	5.467%	$218.264	$218.26	$218.25	$218.30
Purchase #7	$78.26	4.425%	$81.723	$81.72	$81.70	$81.70
7 purchase totals =	$1,009.25		$1,074.5011	$1,074.49	$1,074.45	$1,074.60