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	$35.98	12.766%	$40.5732	$40.57	$40.55	$40.60
Purchase #2	$93.93	7.157%	$100.6526	$100.65	$100.65	$100.70
Purchase #3	$148.34	7.499%	$159.464	$159.46	$159.45	$159.50
Purchase #4	$49.73	8.706%	$54.0595	$54.06	$54.05	$54.10
Purchase #5	$234.93	12.469%	$264.2234	$264.22	$264.20	$264.20
Purchase #6	$209.77	7.685%	$225.8908	$225.89	$225.90	$225.90
Purchase #7	$197.36	3.441%	$204.1512	$204.15	$204.15	$204.20
7 purchase totals =	$970.04		$1,049.0147	$1,049.00	$1,048.95	$1,049.20