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	$172.46	7.775%	$185.8688	$185.87	$185.85	$185.90
Purchase #2	$150.97	12.287%	$169.5197	$169.52	$169.50	$169.50
Purchase #3	$95.82	13.232%	$108.4989	$108.50	$108.50	$108.50
Purchase #4	$28.51	9.819%	$31.3094	$31.31	$31.30	$31.30
Purchase #5	$156.49	5.651%	$165.3332	$165.33	$165.35	$165.30
Purchase #6	$171.35	8.581%	$186.0535	$186.05	$186.05	$186.10
Purchase #7	$54.80	8.398%	$59.4021	$59.40	$59.40	$59.40
7 purchase totals =	$830.40		$905.9856	$905.98	$905.95	$906.00