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	$232.36	13.577%	$263.9075	$263.91	$263.90	$263.90
Purchase #2	$32.33	13.124%	$36.573	$36.57	$36.55	$36.60
Purchase #3	$101.56	9.615%	$111.325	$111.33	$111.35	$111.30
Purchase #4	$6.53	7.737%	$7.0352	$7.04	$7.05	$7.00
Purchase #5	$245.29	8.363%	$265.8036	$265.80	$265.80	$265.80
Purchase #6	$47.90	6.420%	$50.9752	$50.98	$51.00	$51.00
Purchase #7	$120.42	11.712%	$134.5236	$134.52	$134.50	$134.50
7 purchase totals =	$786.39		$870.1431	$870.15	$870.15	$870.10