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	$69.96	6.157%	$74.2674	$74.27	$74.25	$74.30
Purchase #2	$248.91	11.311%	$277.0642	$277.06	$277.05	$277.10
Purchase #3	$117.43	5.451%	$123.8311	$123.83	$123.85	$123.80
Purchase #4	$234.90	11.669%	$262.3105	$262.31	$262.30	$262.30
Purchase #5	$76.73	13.843%	$87.3517	$87.35	$87.35	$87.40
Purchase #6	$156.97	5.512%	$165.6222	$165.62	$165.60	$165.60
Purchase #7	$82.86	7.588%	$89.1474	$89.15	$89.15	$89.10
7 purchase totals =	$987.76		$1,079.5945	$1,079.59	$1,079.55	$1,079.60