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	$102.50	10.166%	$112.9202	$112.92	$112.90	$112.90
Purchase #2	$105.59	5.229%	$111.1113	$111.11	$111.10	$111.10
Purchase #3	$44.88	8.188%	$48.5548	$48.55	$48.55	$48.60
Purchase #4	$233.90	11.708%	$261.285	$261.29	$261.30	$261.30
Purchase #5	$138.73	8.506%	$150.5304	$150.53	$150.55	$150.50
Purchase #6	$49.33	6.562%	$52.567	$52.57	$52.55	$52.60
Purchase #7	$235.86	3.872%	$244.9925	$244.99	$245.00	$245.00
7 purchase totals =	$910.79		$981.9612	$981.96	$981.95	$982.00