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	$56.71	9.817%	$62.2772	$62.28	$62.30	$62.30
Purchase #2	$86.85	3.147%	$89.5832	$89.58	$89.60	$89.60
Purchase #3	$108.91	5.198%	$114.5711	$114.57	$114.55	$114.60
Purchase #4	$64.40	10.858%	$71.3926	$71.39	$71.40	$71.40
Purchase #5	$120.84	10.568%	$133.6104	$133.61	$133.60	$133.60
Purchase #6	$246.96	7.401%	$265.2375	$265.24	$265.25	$265.20
Purchase #7	$48.86	7.564%	$52.5558	$52.56	$52.55	$52.60
7 purchase totals =	$733.53		$789.2278	$789.23	$789.25	$789.30