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	$100.77	8.240%	$109.0734	$109.07	$109.05	$109.10
Purchase #2	$219.90	4.351%	$229.4678	$229.47	$229.45	$229.50
Purchase #3	$67.68	3.854%	$70.2884	$70.29	$70.30	$70.30
Purchase #4	$56.44	4.845%	$59.1745	$59.17	$59.15	$59.20
Purchase #5	$155.90	13.604%	$177.1086	$177.11	$177.10	$177.10
Purchase #6	$80.84	12.514%	$90.9563	$90.96	$90.95	$91.00
Purchase #7	$159.86	7.231%	$171.4195	$171.42	$171.40	$171.40
7 purchase totals =	$841.39		$907.4885	$907.49	$907.40	$907.60