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	$241.69	7.748%	$260.4161	$260.42	$260.40	$260.40
Purchase #2	$79.77	11.730%	$89.127	$89.13	$89.15	$89.10
Purchase #3	$123.36	3.607%	$127.8096	$127.81	$127.80	$127.80
Purchase #4	$241.71	9.188%	$263.9183	$263.92	$263.90	$263.90
Purchase #5	$59.95	13.786%	$68.2147	$68.21	$68.20	$68.20
Purchase #6	$41.61	9.609%	$45.6083	$45.61	$45.60	$45.60
Purchase #7	$150.45	11.858%	$168.2904	$168.29	$168.30	$168.30
7 purchase totals =	$938.54		$1,023.3844	$1,023.39	$1,023.35	$1,023.30