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	$124.25	7.682%	$133.7949	$133.79	$133.80	$133.80
Purchase #2	$72.36	11.206%	$80.4687	$80.47	$80.45	$80.50
Purchase #3	$127.44	8.716%	$138.5477	$138.55	$138.55	$138.50
Purchase #4	$75.98	13.418%	$86.175	$86.18	$86.20	$86.20
Purchase #5	$141.52	6.153%	$150.2277	$150.23	$150.25	$150.20
Purchase #6	$191.57	13.789%	$217.9856	$217.99	$218.00	$218.00
Purchase #7	$240.71	5.445%	$253.8167	$253.82	$253.80	$253.80
7 purchase totals =	$973.83		$1,061.0163	$1,061.03	$1,061.05	$1,061.00