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	$59.71	4.388%	$62.3301	$62.33	$62.35	$62.30
Purchase #2	$220.61	11.454%	$245.8787	$245.88	$245.90	$245.90
Purchase #3	$112.88	9.285%	$123.3609	$123.36	$123.35	$123.40
Purchase #4	$6.64	3.484%	$6.8713	$6.87	$6.85	$6.90
Purchase #5	$183.95	6.816%	$196.488	$196.49	$196.50	$196.50
Purchase #6	$20.85	6.120%	$22.126	$22.13	$22.15	$22.10
Purchase #7	$157.60	4.331%	$164.4257	$164.43	$164.45	$164.40
7 purchase totals =	$762.24		$821.4807	$821.49	$821.55	$821.50