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	$67.35	7.454%	$72.3703	$72.37	$72.35	$72.40
Purchase #2	$209.49	9.486%	$229.3622	$229.36	$229.35	$229.40
Purchase #3	$21.44	3.452%	$22.1801	$22.18	$22.20	$22.20
Purchase #4	$88.51	12.600%	$99.6623	$99.66	$99.65	$99.70
Purchase #5	$152.55	7.759%	$164.3864	$164.39	$164.40	$164.40
Purchase #6	$195.53	12.813%	$220.5833	$220.58	$220.60	$220.60
Purchase #7	$237.78	5.501%	$250.8603	$250.86	$250.85	$250.90
7 purchase totals =	$972.65		$1,059.4049	$1,059.40	$1,059.40	$1,059.60