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	$115.47	7.695%	$124.3554	$124.36	$124.35	$124.40
Purchase #2	$189.28	11.248%	$210.5702	$210.57	$210.55	$210.60
Purchase #3	$41.71	9.323%	$45.5986	$45.60	$45.60	$45.60
Purchase #4	$174.44	12.700%	$196.5939	$196.59	$196.60	$196.60
Purchase #5	$42.43	8.138%	$45.883	$45.88	$45.90	$45.90
Purchase #6	$211.47	13.609%	$240.249	$240.25	$240.25	$240.20
Purchase #7	$17.70	7.769%	$19.0751	$19.08	$19.10	$19.10
7 purchase totals =	$792.50		$882.3252	$882.33	$882.35	$882.40