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	$69.55	4.656%	$72.7882	$72.79	$72.80	$72.80
Purchase #2	$130.38	9.507%	$142.7752	$142.78	$142.80	$142.80
Purchase #3	$12.50	4.717%	$13.0896	$13.09	$13.10	$13.10
Purchase #4	$20.44	4.444%	$21.3484	$21.35	$21.35	$21.30
Purchase #5	$13.57	11.279%	$15.1006	$15.10	$15.10	$15.10
Purchase #6	$231.51	12.138%	$259.6107	$259.61	$259.60	$259.60
Purchase #7	$247.41	6.501%	$263.4941	$263.49	$263.50	$263.50
7 purchase totals =	$725.36		$788.2068	$788.21	$788.25	$788.20