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	$188.71	5.610%	$199.2966	$199.30	$199.30	$199.30
Purchase #2	$20.51	3.841%	$21.2978	$21.30	$21.30	$21.30
Purchase #3	$245.41	6.745%	$261.9629	$261.96	$261.95	$262.00
Purchase #4	$133.42	11.401%	$148.6312	$148.63	$148.65	$148.60
Purchase #5	$180.73	4.525%	$188.908	$188.91	$188.90	$188.90
Purchase #6	$46.84	11.521%	$52.2364	$52.24	$52.25	$52.20
Purchase #7	$218.42	4.186%	$227.5631	$227.56	$227.55	$227.60
7 purchase totals =	$1,034.04		$1,099.8960	$1,099.90	$1,099.90	$1,099.90