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	$81.87	11.319%	$91.1369	$91.14	$91.15	$91.10
Purchase #2	$106.96	4.233%	$111.4876	$111.49	$111.50	$111.50
Purchase #3	$142.60	7.688%	$153.5631	$153.56	$153.55	$153.60
Purchase #4	$117.86	4.117%	$122.7123	$122.71	$122.70	$122.70
Purchase #5	$21.59	9.481%	$23.6369	$23.64	$23.65	$23.60
Purchase #6	$187.89	4.615%	$196.5611	$196.56	$196.55	$196.60
Purchase #7	$73.39	11.647%	$81.9377	$81.94	$81.95	$81.90
7 purchase totals =	$732.16		$781.0356	$781.04	$781.05	$781.00