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	$41.93	9.142%	$45.7632	$45.76	$45.75	$45.80
Purchase #2	$88.82	8.537%	$96.4026	$96.40	$96.40	$96.40
Purchase #3	$142.91	11.440%	$159.2589	$159.26	$159.25	$159.30
Purchase #4	$176.54	7.693%	$190.1212	$190.12	$190.10	$190.10
Purchase #5	$121.61	9.351%	$132.9818	$132.98	$133.00	$133.00
Purchase #6	$250.62	8.522%	$271.9778	$271.98	$272.00	$272.00
Purchase #7	$102.34	3.235%	$105.6507	$105.65	$105.65	$105.70
7 purchase totals =	$924.77		$1,002.1562	$1,002.15	$1,002.15	$1,002.30