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	$192.69	3.354%	$199.1528	$199.15	$199.15	$199.20
Purchase #2	$243.87	5.220%	$256.6	$256.60	$256.60	$256.60
Purchase #3	$10.74	3.851%	$11.1536	$11.15	$11.15	$11.20
Purchase #4	$224.52	9.184%	$245.1399	$245.14	$245.15	$245.10
Purchase #5	$61.84	11.660%	$69.0505	$69.05	$69.05	$69.10
Purchase #6	$139.59	3.674%	$144.7185	$144.72	$144.70	$144.70
Purchase #7	$147.61	11.524%	$164.6206	$164.62	$164.60	$164.60
7 purchase totals =	$1,020.86		$1,090.4359	$1,090.43	$1,090.40	$1,090.50