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	$84.27	9.518%	$92.2908	$92.29	$92.30	$92.30
Purchase #2	$148.29	7.557%	$159.4963	$159.50	$159.50	$159.50
Purchase #3	$148.84	6.696%	$158.8063	$158.81	$158.80	$158.80
Purchase #4	$42.80	9.376%	$46.8129	$46.81	$46.80	$46.80
Purchase #5	$91.98	8.300%	$99.6143	$99.61	$99.60	$99.60
Purchase #6	$210.37	9.856%	$231.1041	$231.10	$231.10	$231.10
Purchase #7	$130.71	5.468%	$137.8572	$137.86	$137.85	$137.90
7 purchase totals =	$857.26		$925.9819	$925.98	$925.95	$926.00