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	$149.41	4.303%	$155.8391	$155.84	$155.85	$155.80
Purchase #2	$223.89	4.347%	$233.6225	$233.62	$233.60	$233.60
Purchase #3	$16.89	7.289%	$18.1211	$18.12	$18.10	$18.10
Purchase #4	$220.89	13.385%	$250.4561	$250.46	$250.45	$250.50
Purchase #5	$170.41	8.535%	$184.9545	$184.95	$184.95	$185.00
Purchase #6	$27.80	8.854%	$30.2614	$30.26	$30.25	$30.30
Purchase #7	$126.44	3.777%	$131.2156	$131.22	$131.20	$131.20
7 purchase totals =	$935.73		$1,004.4703	$1,004.47	$1,004.40	$1,004.50