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	$35.82	3.169%	$36.9551	$36.96	$36.95	$37.00
Purchase #2	$57.32	3.124%	$59.1107	$59.11	$59.10	$59.10
Purchase #3	$227.56	5.591%	$240.2829	$240.28	$240.30	$240.30
Purchase #4	$17.71	6.820%	$18.9178	$18.92	$18.90	$18.90
Purchase #5	$7.53	12.706%	$8.4868	$8.49	$8.50	$8.50
Purchase #6	$36.49	13.401%	$41.38	$41.38	$41.40	$41.40
Purchase #7	$105.86	8.295%	$114.6411	$114.64	$114.65	$114.60
7 purchase totals =	$488.29		$519.7744	$519.78	$519.80	$519.80