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	$189.97	10.226%	$209.3963	$209.40	$209.40	$209.40
Purchase #2	$50.83	6.834%	$54.3037	$54.30	$54.30	$54.30
Purchase #3	$155.89	4.495%	$162.8973	$162.90	$162.90	$162.90
Purchase #4	$164.37	8.224%	$177.8878	$177.89	$177.90	$177.90
Purchase #5	$30.30	9.845%	$33.283	$33.28	$33.30	$33.30
Purchase #6	$63.55	6.765%	$67.8492	$67.85	$67.85	$67.80
Purchase #7	$141.79	4.861%	$148.6824	$148.68	$148.70	$148.70
7 purchase totals =	$796.70		$854.2997	$854.30	$854.35	$854.30