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	$228.55	6.607%	$243.6503	$243.65	$243.65	$243.70
Purchase #2	$172.96	5.756%	$182.9156	$182.92	$182.90	$182.90
Purchase #3	$54.59	8.128%	$59.0271	$59.03	$59.05	$59.00
Purchase #4	$168.31	10.366%	$185.757	$185.76	$185.75	$185.80
Purchase #5	$203.73	12.153%	$228.4893	$228.49	$228.50	$228.50
Purchase #6	$82.97	12.607%	$93.43	$93.43	$93.45	$93.40
Purchase #7	$97.39	5.202%	$102.4562	$102.46	$102.45	$102.50
7 purchase totals =	$1,008.50		$1,095.7255	$1,095.74	$1,095.75	$1,095.80