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	$83.47	8.704%	$90.7352	$90.74	$90.75	$90.70
Purchase #2	$184.53	6.223%	$196.0133	$196.01	$196.00	$196.00
Purchase #3	$38.59	7.473%	$41.4738	$41.47	$41.45	$41.50
Purchase #4	$101.50	9.664%	$111.309	$111.31	$111.30	$111.30
Purchase #5	$130.93	12.495%	$147.2897	$147.29	$147.30	$147.30
Purchase #6	$79.83	6.815%	$85.2704	$85.27	$85.25	$85.30
Purchase #7	$74.62	5.206%	$78.5047	$78.50	$78.50	$78.50
7 purchase totals =	$693.47		$750.5961	$750.59	$750.55	$750.60