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	$67.72	7.546%	$72.8302	$72.83	$72.85	$72.80
Purchase #2	$45.99	13.216%	$52.068	$52.07	$52.05	$52.10
Purchase #3	$106.96	10.874%	$118.5908	$118.59	$118.60	$118.60
Purchase #4	$81.49	8.843%	$88.6962	$88.70	$88.70	$88.70
Purchase #5	$79.37	13.367%	$89.9794	$89.98	$90.00	$90.00
Purchase #6	$66.86	7.798%	$72.0737	$72.07	$72.05	$72.10
Purchase #7	$187.90	8.832%	$204.4953	$204.50	$204.50	$204.50
7 purchase totals =	$636.29		$698.7336	$698.74	$698.75	$698.80