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	$229.67	11.862%	$256.9135	$256.91	$256.90	$256.90
Purchase #2	$30.92	3.686%	$32.0597	$32.06	$32.05	$32.10
Purchase #3	$168.81	9.364%	$184.6174	$184.62	$184.60	$184.60
Purchase #4	$141.99	13.332%	$160.9201	$160.92	$160.90	$160.90
Purchase #5	$67.60	7.437%	$72.6274	$72.63	$72.65	$72.60
Purchase #6	$227.94	7.818%	$245.7603	$245.76	$245.75	$245.80
Purchase #7	$164.86	3.793%	$171.1131	$171.11	$171.10	$171.10
7 purchase totals =	$1,031.79		$1,124.0115	$1,124.01	$1,123.95	$1,124.00