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	$149.34	13.797%	$169.9444	$169.94	$169.95	$169.90
Purchase #2	$166.97	7.435%	$179.3842	$179.38	$179.40	$179.40
Purchase #3	$237.92	5.238%	$250.3822	$250.38	$250.40	$250.40
Purchase #4	$69.83	3.745%	$72.4451	$72.45	$72.45	$72.40
Purchase #5	$125.64	11.268%	$139.7971	$139.80	$139.80	$139.80
Purchase #6	$164.47	6.711%	$175.5076	$175.51	$175.50	$175.50
Purchase #7	$69.64	13.494%	$79.0372	$79.04	$79.05	$79.00
7 purchase totals =	$983.81		$1,066.4978	$1,066.50	$1,066.55	$1,066.40