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	$85.59	12.165%	$96.002	$96.00	$96.00	$96.00
Purchase #2	$25.75	7.633%	$27.7155	$27.72	$27.70	$27.70
Purchase #3	$242.65	11.560%	$270.7003	$270.70	$270.70	$270.70
Purchase #4	$42.59	4.748%	$44.6122	$44.61	$44.60	$44.60
Purchase #5	$61.39	4.475%	$64.1372	$64.14	$64.15	$64.10
Purchase #6	$80.79	3.380%	$83.5207	$83.52	$83.50	$83.50
Purchase #7	$31.86	6.512%	$33.9347	$33.93	$33.95	$33.90
7 purchase totals =	$570.62		$620.6226	$620.62	$620.60	$620.50