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	$83.83	9.714%	$91.9732	$91.97	$91.95	$92.00
Purchase #2	$68.46	5.730%	$72.3828	$72.38	$72.40	$72.40
Purchase #3	$131.64	6.779%	$140.5639	$140.56	$140.55	$140.60
Purchase #4	$50.71	11.405%	$56.4935	$56.49	$56.50	$56.50
Purchase #5	$63.86	4.397%	$66.6679	$66.67	$66.65	$66.70
Purchase #6	$61.96	10.859%	$68.6882	$68.69	$68.70	$68.70
Purchase #7	$35.73	7.873%	$38.543	$38.54	$38.55	$38.50
7 purchase totals =	$496.19		$535.3125	$535.30	$535.30	$535.40