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	$87.71	11.408%	$97.716	$97.72	$97.70	$97.70
Purchase #2	$82.56	3.610%	$85.5404	$85.54	$85.55	$85.50
Purchase #3	$246.33	8.846%	$268.1204	$268.12	$268.10	$268.10
Purchase #4	$70.80	4.375%	$73.8975	$73.90	$73.90	$73.90
Purchase #5	$36.94	13.319%	$41.86	$41.86	$41.85	$41.90
Purchase #6	$39.89	12.544%	$44.8938	$44.89	$44.90	$44.90
Purchase #7	$165.38	5.742%	$174.8761	$174.88	$174.90	$174.90
7 purchase totals =	$729.61		$786.9042	$786.91	$786.90	$786.90