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	$177.60	4.546%	$185.6737	$185.67	$185.65	$185.70
Purchase #2	$123.56	8.688%	$134.2949	$134.29	$134.30	$134.30
Purchase #3	$109.25	8.253%	$118.2664	$118.27	$118.25	$118.30
Purchase #4	$148.96	12.814%	$168.0477	$168.05	$168.05	$168.00
Purchase #5	$46.27	3.265%	$47.7807	$47.78	$47.80	$47.80
Purchase #6	$80.46	10.738%	$89.0998	$89.10	$89.10	$89.10
Purchase #7	$17.49	11.377%	$19.4798	$19.48	$19.50	$19.50
7 purchase totals =	$703.59		$762.6430	$762.64	$762.65	$762.70