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	$158.99	7.623%	$171.1098	$171.11	$171.10	$171.10
Purchase #2	$79.55	10.496%	$87.8996	$87.90	$87.90	$87.90
Purchase #3	$155.75	10.707%	$172.4262	$172.43	$172.45	$172.40
Purchase #4	$202.35	12.368%	$227.3766	$227.38	$227.40	$227.40
Purchase #5	$231.32	5.728%	$244.57	$244.57	$244.55	$244.60
Purchase #6	$168.92	3.157%	$174.2528	$174.25	$174.25	$174.30
Purchase #7	$17.98	4.486%	$18.7866	$18.79	$18.80	$18.80
7 purchase totals =	$1,014.86		$1,096.4216	$1,096.43	$1,096.45	$1,096.50