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	$185.85	13.265%	$210.503	$210.50	$210.50	$210.50
Purchase #2	$89.90	12.679%	$101.2984	$101.30	$101.30	$101.30
Purchase #3	$191.26	6.769%	$204.2064	$204.21	$204.20	$204.20
Purchase #4	$178.51	11.295%	$198.6727	$198.67	$198.65	$198.70
Purchase #5	$79.39	12.425%	$89.2542	$89.25	$89.25	$89.30
Purchase #6	$91.83	4.493%	$95.9559	$95.96	$95.95	$96.00
Purchase #7	$158.81	5.400%	$167.3857	$167.39	$167.40	$167.40
7 purchase totals =	$975.55		$1,067.2763	$1,067.28	$1,067.25	$1,067.40