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	$121.45	9.229%	$132.6586	$132.66	$132.65	$132.70
Purchase #2	$142.27	8.627%	$154.5436	$154.54	$154.55	$154.50
Purchase #3	$162.33	8.147%	$175.555	$175.56	$175.55	$175.60
Purchase #4	$191.62	7.216%	$205.4473	$205.45	$205.45	$205.40
Purchase #5	$30.44	9.166%	$33.2301	$33.23	$33.25	$33.20
Purchase #6	$43.75	4.628%	$45.7748	$45.77	$45.75	$45.80
Purchase #7	$144.41	5.702%	$152.6443	$152.64	$152.65	$152.60
7 purchase totals =	$836.27		$899.8537	$899.85	$899.85	$899.80