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	$169.26	9.363%	$185.1078	$185.11	$185.10	$185.10
Purchase #2	$70.29	4.601%	$73.524	$73.52	$73.50	$73.50
Purchase #3	$212.56	13.788%	$241.8678	$241.87	$241.85	$241.90
Purchase #4	$144.82	4.292%	$151.0357	$151.04	$151.05	$151.00
Purchase #5	$119.81	7.294%	$128.5489	$128.55	$128.55	$128.50
Purchase #6	$33.52	12.801%	$37.8109	$37.81	$37.80	$37.80
Purchase #7	$229.87	10.139%	$253.1765	$253.18	$253.20	$253.20
7 purchase totals =	$980.13		$1,071.0716	$1,071.08	$1,071.05	$1,071.00