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	$64.86	4.480%	$67.7657	$67.77	$67.75	$67.80
Purchase #2	$59.76	5.610%	$63.1125	$63.11	$63.10	$63.10
Purchase #3	$157.96	3.847%	$164.0367	$164.04	$164.05	$164.00
Purchase #4	$71.92	6.781%	$76.7969	$76.80	$76.80	$76.80
Purchase #5	$89.34	11.488%	$99.6034	$99.60	$99.60	$99.60
Purchase #6	$36.66	8.277%	$39.6943	$39.69	$39.70	$39.70
Purchase #7	$216.33	10.314%	$238.6423	$238.64	$238.65	$238.60
7 purchase totals =	$696.83		$749.6518	$749.65	$749.65	$749.60