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	$70.25	11.503%	$78.3309	$78.33	$78.35	$78.30
Purchase #2	$169.41	13.668%	$192.565	$192.57	$192.55	$192.60
Purchase #3	$52.78	4.832%	$55.3303	$55.33	$55.35	$55.30
Purchase #4	$142.88	5.607%	$150.8913	$150.89	$150.90	$150.90
Purchase #5	$53.40	5.589%	$56.3845	$56.38	$56.40	$56.40
Purchase #6	$153.74	11.406%	$171.2756	$171.28	$171.30	$171.30
Purchase #7	$214.91	6.190%	$228.2129	$228.21	$228.20	$228.20
7 purchase totals =	$857.37		$932.9905	$932.99	$933.05	$933.00