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	$119.72	13.566%	$135.9612	$135.96	$135.95	$136.00
Purchase #2	$6.88	8.514%	$7.4658	$7.47	$7.45	$7.50
Purchase #3	$189.82	3.488%	$196.4409	$196.44	$196.45	$196.40
Purchase #4	$199.33	11.536%	$222.3247	$222.32	$222.30	$222.30
Purchase #5	$113.99	8.494%	$123.6723	$123.67	$123.65	$123.70
Purchase #6	$96.53	9.439%	$105.6415	$105.64	$105.65	$105.60
Purchase #7	$148.62	9.304%	$162.4476	$162.45	$162.45	$162.40
7 purchase totals =	$874.89		$953.9540	$953.95	$953.90	$953.90