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	$122.35	10.761%	$135.5161	$135.52	$135.50	$135.50
Purchase #2	$212.55	10.498%	$234.8635	$234.86	$234.85	$234.90
Purchase #3	$42.68	9.865%	$46.8904	$46.89	$46.90	$46.90
Purchase #4	$123.25	3.568%	$127.6476	$127.65	$127.65	$127.60
Purchase #5	$191.47	12.317%	$215.0534	$215.05	$215.05	$215.10
Purchase #6	$131.82	12.480%	$148.2711	$148.27	$148.25	$148.30
Purchase #7	$155.79	3.401%	$161.0884	$161.09	$161.10	$161.10
7 purchase totals =	$979.91		$1,069.3305	$1,069.33	$1,069.30	$1,069.40