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	$125.54	7.228%	$134.614	$134.61	$134.60	$134.60
Purchase #2	$79.37	9.456%	$86.8752	$86.88	$86.90	$86.90
Purchase #3	$156.50	9.345%	$171.1249	$171.12	$171.10	$171.10
Purchase #4	$42.44	9.554%	$46.4947	$46.49	$46.50	$46.50
Purchase #5	$25.95	5.804%	$27.4561	$27.46	$27.45	$27.50
Purchase #6	$130.44	8.105%	$141.0122	$141.01	$141.00	$141.00
Purchase #7	$179.41	4.428%	$187.3543	$187.35	$187.35	$187.40
7 purchase totals =	$739.65		$794.9314	$794.92	$794.90	$795.00