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	$79.41	7.709%	$85.5317	$85.53	$85.55	$85.50
Purchase #2	$139.74	10.813%	$154.8501	$154.85	$154.85	$154.90
Purchase #3	$103.87	8.578%	$112.78	$112.78	$112.80	$112.80
Purchase #4	$38.33	4.225%	$39.9494	$39.95	$39.95	$39.90
Purchase #5	$18.65	11.333%	$20.7636	$20.76	$20.75	$20.80
Purchase #6	$212.93	4.865%	$223.289	$223.29	$223.30	$223.30
Purchase #7	$74.80	4.816%	$78.4024	$78.40	$78.40	$78.40
7 purchase totals =	$667.73		$715.5662	$715.56	$715.60	$715.60