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	$182.79	9.524%	$200.1989	$200.20	$200.20	$200.20
Purchase #2	$69.76	3.797%	$72.4088	$72.41	$72.40	$72.40
Purchase #3	$172.86	6.143%	$183.4788	$183.48	$183.50	$183.50
Purchase #4	$199.33	10.789%	$220.8357	$220.84	$220.85	$220.80
Purchase #5	$38.91	8.797%	$42.3329	$42.33	$42.35	$42.30
Purchase #6	$35.30	12.594%	$39.7457	$39.75	$39.75	$39.70
Purchase #7	$89.80	10.503%	$99.2317	$99.23	$99.25	$99.20
7 purchase totals =	$788.75		$858.2325	$858.24	$858.30	$858.10