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	$178.72	9.445%	$195.6001	$195.60	$195.60	$195.60
Purchase #2	$41.68	9.115%	$45.4791	$45.48	$45.50	$45.50
Purchase #3	$171.40	12.718%	$193.1987	$193.20	$193.20	$193.20
Purchase #4	$150.95	7.435%	$162.1731	$162.17	$162.15	$162.20
Purchase #5	$33.69	10.632%	$37.2719	$37.27	$37.25	$37.30
Purchase #6	$50.70	6.339%	$53.9139	$53.91	$53.90	$53.90
Purchase #7	$42.96	13.554%	$48.7828	$48.78	$48.80	$48.80
7 purchase totals =	$670.10		$736.4196	$736.41	$736.40	$736.50