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	$176.27	9.407%	$192.8517	$192.85	$192.85	$192.90
Purchase #2	$149.45	4.265%	$155.824	$155.82	$155.80	$155.80
Purchase #3	$42.25	7.650%	$45.4821	$45.48	$45.50	$45.50
Purchase #4	$226.96	9.496%	$248.5121	$248.51	$248.50	$248.50
Purchase #5	$112.33	6.649%	$119.7988	$119.80	$119.80	$119.80
Purchase #6	$50.91	9.186%	$55.5866	$55.59	$55.60	$55.60
Purchase #7	$84.53	11.675%	$94.3989	$94.40	$94.40	$94.40
7 purchase totals =	$842.70		$912.4542	$912.45	$912.45	$912.50