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	$108.73	9.293%	$118.8343	$118.83	$118.85	$118.80
Purchase #2	$10.44	9.342%	$11.4153	$11.42	$11.40	$11.40
Purchase #3	$144.86	11.363%	$161.3204	$161.32	$161.30	$161.30
Purchase #4	$207.49	7.708%	$223.4833	$223.48	$223.50	$223.50
Purchase #5	$38.76	9.737%	$42.5341	$42.53	$42.55	$42.50
Purchase #6	$55.43	7.190%	$59.4154	$59.42	$59.40	$59.40
Purchase #7	$172.59	6.405%	$183.6444	$183.64	$183.65	$183.60
7 purchase totals =	$738.30		$800.6472	$800.64	$800.65	$800.50