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	$89.71	7.541%	$96.475	$96.48	$96.50	$96.50
Purchase #2	$233.87	13.206%	$264.7549	$264.75	$264.75	$264.80
Purchase #3	$196.75	12.295%	$220.9404	$220.94	$220.95	$220.90
Purchase #4	$46.32	8.478%	$50.247	$50.25	$50.25	$50.20
Purchase #5	$43.56	11.621%	$48.6221	$48.62	$48.60	$48.60
Purchase #6	$243.54	7.683%	$262.2512	$262.25	$262.25	$262.30
Purchase #7	$233.56	12.697%	$263.2151	$263.22	$263.20	$263.20
7 purchase totals =	$1,087.31		$1,206.5057	$1,206.51	$1,206.50	$1,206.50