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	$70.72	10.626%	$78.2347	$78.23	$78.25	$78.20
Purchase #2	$87.68	3.686%	$90.9119	$90.91	$90.90	$90.90
Purchase #3	$120.68	9.154%	$131.727	$131.73	$131.75	$131.70
Purchase #4	$99.40	9.831%	$109.172	$109.17	$109.15	$109.20
Purchase #5	$171.70	3.709%	$178.0684	$178.07	$178.05	$178.10
Purchase #6	$173.49	6.596%	$184.9334	$184.93	$184.95	$184.90
Purchase #7	$164.48	9.800%	$180.599	$180.60	$180.60	$180.60
7 purchase totals =	$888.15		$953.6464	$953.64	$953.65	$953.60