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	$168.82	7.197%	$180.97	$180.97	$180.95	$181.00
Purchase #2	$161.55	4.597%	$168.9765	$168.98	$169.00	$169.00
Purchase #3	$157.40	9.115%	$171.747	$171.75	$171.75	$171.70
Purchase #4	$138.89	9.799%	$152.4998	$152.50	$152.50	$152.50
Purchase #5	$198.25	6.374%	$210.8865	$210.89	$210.90	$210.90
Purchase #6	$20.31	4.696%	$21.2638	$21.26	$21.25	$21.30
Purchase #7	$52.96	9.312%	$57.8916	$57.89	$57.90	$57.90
7 purchase totals =	$898.18		$964.2352	$964.24	$964.25	$964.30