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	$83.91	10.495%	$92.7164	$92.72	$92.70	$92.70
Purchase #2	$87.77	7.669%	$94.5011	$94.50	$94.50	$94.50
Purchase #3	$8.56	3.119%	$8.827	$8.83	$8.85	$8.80
Purchase #4	$41.33	3.642%	$42.8352	$42.84	$42.85	$42.80
Purchase #5	$191.59	5.718%	$202.5451	$202.55	$202.55	$202.50
Purchase #6	$112.89	13.668%	$128.3198	$128.32	$128.30	$128.30
Purchase #7	$184.50	3.807%	$191.5239	$191.52	$191.50	$191.50
7 purchase totals =	$710.55		$761.2685	$761.28	$761.25	$761.10