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	$169.62	12.850%	$191.4162	$191.42	$191.40	$191.40
Purchase #2	$197.65	9.234%	$215.901	$215.90	$215.90	$215.90
Purchase #3	$50.80	3.625%	$52.6415	$52.64	$52.65	$52.60
Purchase #4	$153.34	6.136%	$162.7489	$162.75	$162.75	$162.70
Purchase #5	$185.73	5.595%	$196.1216	$196.12	$196.10	$196.10
Purchase #6	$136.63	8.776%	$148.6206	$148.62	$148.60	$148.60
Purchase #7	$142.37	5.419%	$150.085	$150.09	$150.10	$150.10
7 purchase totals =	$1,036.14		$1,117.5348	$1,117.54	$1,117.50	$1,117.40