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	$134.30	10.662%	$148.6191	$148.62	$148.60	$148.60
Purchase #2	$221.88	6.370%	$236.0138	$236.01	$236.00	$236.00
Purchase #3	$165.40	3.854%	$171.7745	$171.77	$171.75	$171.80
Purchase #4	$235.31	6.343%	$250.2357	$250.24	$250.25	$250.20
Purchase #5	$244.76	4.643%	$256.1242	$256.12	$256.10	$256.10
Purchase #6	$177.64	10.739%	$196.7168	$196.72	$196.70	$196.70
Purchase #7	$144.64	4.256%	$150.7959	$150.80	$150.80	$150.80
7 purchase totals =	$1,323.93		$1,410.2800	$1,410.28	$1,410.20	$1,410.20