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	$94.62	12.869%	$106.7966	$106.80	$106.80	$106.80
Purchase #2	$216.87	11.815%	$242.4932	$242.49	$242.50	$242.50
Purchase #3	$143.95	9.809%	$158.0701	$158.07	$158.05	$158.10
Purchase #4	$158.51	12.674%	$178.5996	$178.60	$178.60	$178.60
Purchase #5	$158.76	3.479%	$164.2833	$164.28	$164.30	$164.30
Purchase #6	$84.60	8.671%	$91.9357	$91.94	$91.95	$91.90
Purchase #7	$78.87	13.851%	$89.7943	$89.79	$89.80	$89.80
7 purchase totals =	$936.18		$1,031.9728	$1,031.97	$1,032.00	$1,032.00