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	$66.84	8.238%	$72.3463	$72.35	$72.35	$72.30
Purchase #2	$145.46	13.370%	$164.908	$164.91	$164.90	$164.90
Purchase #3	$185.36	7.146%	$198.6058	$198.61	$198.60	$198.60
Purchase #4	$188.97	12.297%	$212.2076	$212.21	$212.20	$212.20
Purchase #5	$74.54	5.376%	$78.5473	$78.55	$78.55	$78.50
Purchase #6	$55.25	13.114%	$62.4955	$62.50	$62.50	$62.50
Purchase #7	$42.50	9.452%	$46.5171	$46.52	$46.50	$46.50
7 purchase totals =	$758.92		$835.6276	$835.65	$835.60	$835.50