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	$191.95	10.123%	$211.3811	$211.38	$211.40	$211.40
Purchase #2	$228.40	7.434%	$245.3793	$245.38	$245.40	$245.40
Purchase #3	$219.55	13.435%	$249.0465	$249.05	$249.05	$249.00
Purchase #4	$100.37	9.268%	$109.6723	$109.67	$109.65	$109.70
Purchase #5	$79.37	12.870%	$89.5849	$89.58	$89.60	$89.60
Purchase #6	$67.32	12.226%	$75.5505	$75.55	$75.55	$75.60
Purchase #7	$83.54	13.791%	$95.061	$95.06	$95.05	$95.10
7 purchase totals =	$970.50		$1,075.6756	$1,075.67	$1,075.70	$1,075.80