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	$95.96	3.384%	$99.2073	$99.21	$99.20	$99.20
Purchase #2	$216.84	4.313%	$226.1923	$226.19	$226.20	$226.20
Purchase #3	$145.27	5.246%	$152.8909	$152.89	$152.90	$152.90
Purchase #4	$72.33	7.155%	$77.5052	$77.51	$77.50	$77.50
Purchase #5	$139.98	8.839%	$152.3528	$152.35	$152.35	$152.40
Purchase #6	$95.89	3.698%	$99.436	$99.44	$99.45	$99.40
Purchase #7	$188.54	7.281%	$202.2676	$202.27	$202.25	$202.30
7 purchase totals =	$954.81		$1,009.8521	$1,009.86	$1,009.85	$1,009.90