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	$82.84	10.193%	$91.2839	$91.28	$91.30	$91.30
Purchase #2	$148.89	10.530%	$164.5681	$164.57	$164.55	$164.60
Purchase #3	$113.82	3.213%	$117.477	$117.48	$117.50	$117.50
Purchase #4	$62.74	6.107%	$66.5715	$66.57	$66.55	$66.60
Purchase #5	$247.94	7.238%	$265.8859	$265.89	$265.90	$265.90
Purchase #6	$128.87	12.705%	$145.2429	$145.24	$145.25	$145.20
Purchase #7	$243.32	11.787%	$272.0001	$272.00	$272.00	$272.00
7 purchase totals =	$1,028.42		$1,123.0294	$1,123.03	$1,123.05	$1,123.10