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	$133.37	13.175%	$150.9415	$150.94	$150.95	$150.90
Purchase #2	$231.42	5.361%	$243.8264	$243.83	$243.85	$243.80
Purchase #3	$162.78	4.601%	$170.2695	$170.27	$170.25	$170.30
Purchase #4	$150.33	8.263%	$162.7518	$162.75	$162.75	$162.80
Purchase #5	$236.49	11.133%	$262.8184	$262.82	$262.80	$262.80
Purchase #6	$63.25	9.537%	$69.2822	$69.28	$69.30	$69.30
Purchase #7	$38.52	11.229%	$42.8454	$42.85	$42.85	$42.80
7 purchase totals =	$1,016.16		$1,102.7352	$1,102.74	$1,102.75	$1,102.70