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	$142.45	4.587%	$148.9842	$148.98	$149.00	$149.00
Purchase #2	$110.81	8.121%	$119.8089	$119.81	$119.80	$119.80
Purchase #3	$219.34	8.769%	$238.5739	$238.57	$238.55	$238.60
Purchase #4	$232.41	9.837%	$255.2722	$255.27	$255.25	$255.30
Purchase #5	$93.87	7.455%	$100.868	$100.87	$100.85	$100.90
Purchase #6	$178.74	11.539%	$199.3648	$199.36	$199.35	$199.40
Purchase #7	$88.46	12.863%	$99.8386	$99.84	$99.85	$99.80
7 purchase totals =	$1,066.08		$1,162.7106	$1,162.70	$1,162.65	$1,162.80