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	$57.50	3.326%	$59.4125	$59.41	$59.40	$59.40
Purchase #2	$201.44	12.428%	$226.475	$226.48	$226.50	$226.50
Purchase #3	$31.60	10.201%	$34.8235	$34.82	$34.80	$34.80
Purchase #4	$219.71	6.656%	$234.3339	$234.33	$234.35	$234.30
Purchase #5	$88.61	6.799%	$94.6346	$94.63	$94.65	$94.60
Purchase #6	$78.94	5.178%	$83.0275	$83.03	$83.05	$83.00
Purchase #7	$50.38	5.786%	$53.295	$53.30	$53.30	$53.30
7 purchase totals =	$728.18		$786.0020	$786.00	$786.05	$785.90