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	$168.26	10.224%	$185.4629	$185.46	$185.45	$185.50
Purchase #2	$137.89	5.821%	$145.9166	$145.92	$145.90	$145.90
Purchase #3	$193.30	10.125%	$212.8716	$212.87	$212.85	$212.90
Purchase #4	$119.25	9.518%	$130.6002	$130.60	$130.60	$130.60
Purchase #5	$221.36	13.321%	$250.8474	$250.85	$250.85	$250.80
Purchase #6	$174.43	6.199%	$185.2429	$185.24	$185.25	$185.20
Purchase #7	$55.28	6.662%	$58.9628	$58.96	$58.95	$59.00
7 purchase totals =	$1,069.77		$1,169.9044	$1,169.90	$1,169.85	$1,169.90