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	$42.76	3.606%	$44.3019	$44.30	$44.30	$44.30
Purchase #2	$223.29	9.486%	$244.4713	$244.47	$244.45	$244.50
Purchase #3	$187.72	3.737%	$194.7351	$194.74	$194.75	$194.70
Purchase #4	$136.49	4.695%	$142.8982	$142.90	$142.90	$142.90
Purchase #5	$87.42	3.312%	$90.3154	$90.32	$90.30	$90.30
Purchase #6	$179.65	10.338%	$198.2222	$198.22	$198.20	$198.20
Purchase #7	$151.78	4.279%	$158.2747	$158.27	$158.25	$158.30
7 purchase totals =	$1,009.11		$1,073.2188	$1,073.22	$1,073.15	$1,073.20