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	$107.40	3.405%	$111.057	$111.06	$111.05	$111.10
Purchase #2	$240.91	7.344%	$258.6024	$258.60	$258.60	$258.60
Purchase #3	$218.32	3.470%	$225.8957	$225.90	$225.90	$225.90
Purchase #4	$93.79	12.794%	$105.7895	$105.79	$105.80	$105.80
Purchase #5	$122.30	7.858%	$131.9103	$131.91	$131.90	$131.90
Purchase #6	$53.93	7.726%	$58.0966	$58.10	$58.10	$58.10
Purchase #7	$176.64	11.526%	$196.9995	$197.00	$197.00	$197.00
7 purchase totals =	$1,013.29		$1,088.3510	$1,088.36	$1,088.35	$1,088.40