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	$37.27	12.117%	$41.786	$41.79	$41.80	$41.80
Purchase #2	$24.91	13.596%	$28.2968	$28.30	$28.30	$28.30
Purchase #3	$178.72	3.734%	$185.3934	$185.39	$185.40	$185.40
Purchase #4	$51.58	11.649%	$57.5886	$57.59	$57.60	$57.60
Purchase #5	$239.36	9.228%	$261.4481	$261.45	$261.45	$261.40
Purchase #6	$132.75	9.121%	$144.8581	$144.86	$144.85	$144.90
Purchase #7	$156.42	12.295%	$175.6518	$175.65	$175.65	$175.70
7 purchase totals =	$821.01		$895.0228	$895.03	$895.05	$895.10