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	$181.72	8.158%	$196.5447	$196.54	$196.55	$196.50
Purchase #2	$242.45	13.135%	$274.2958	$274.30	$274.30	$274.30
Purchase #3	$169.92	11.167%	$188.895	$188.90	$188.90	$188.90
Purchase #4	$56.38	9.264%	$61.603	$61.60	$61.60	$61.60
Purchase #5	$94.85	12.498%	$106.7044	$106.70	$106.70	$106.70
Purchase #6	$35.98	4.107%	$37.4577	$37.46	$37.45	$37.50
Purchase #7	$16.83	7.782%	$18.1397	$18.14	$18.15	$18.10
7 purchase totals =	$798.13		$883.6403	$883.64	$883.65	$883.60