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	$89.73	6.557%	$95.6136	$95.61	$95.60	$95.60
Purchase #2	$128.61	10.870%	$142.5899	$142.59	$142.60	$142.60
Purchase #3	$174.43	11.342%	$194.2139	$194.21	$194.20	$194.20
Purchase #4	$234.90	6.227%	$249.5272	$249.53	$249.55	$249.50
Purchase #5	$148.66	11.255%	$165.3917	$165.39	$165.40	$165.40
Purchase #6	$111.38	13.343%	$126.2414	$126.24	$126.25	$126.20
Purchase #7	$207.80	8.400%	$225.2552	$225.26	$225.25	$225.30
7 purchase totals =	$1,095.51		$1,198.8329	$1,198.83	$1,198.85	$1,198.80