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	$219.91	10.182%	$242.3012	$242.30	$242.30	$242.30
Purchase #2	$47.37	7.421%	$50.8853	$50.89	$50.90	$50.90
Purchase #3	$11.66	9.780%	$12.8003	$12.80	$12.80	$12.80
Purchase #4	$191.37	11.246%	$212.8915	$212.89	$212.90	$212.90
Purchase #5	$107.78	9.322%	$117.8273	$117.83	$117.85	$117.80
Purchase #6	$50.25	7.736%	$54.1373	$54.14	$54.15	$54.10
Purchase #7	$62.90	7.437%	$67.5779	$67.58	$67.60	$67.60
7 purchase totals =	$691.24		$758.4208	$758.43	$758.50	$758.40