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	$242.59	10.849%	$268.9086	$268.91	$268.90	$268.90
Purchase #2	$56.64	5.537%	$59.7762	$59.78	$59.80	$59.80
Purchase #3	$186.90	9.507%	$204.6686	$204.67	$204.65	$204.70
Purchase #4	$219.89	9.320%	$240.3837	$240.38	$240.40	$240.40
Purchase #5	$28.88	12.490%	$32.4871	$32.49	$32.50	$32.50
Purchase #6	$180.62	5.857%	$191.1989	$191.20	$191.20	$191.20
Purchase #7	$176.61	13.325%	$200.1433	$200.14	$200.15	$200.10
7 purchase totals =	$1,092.13		$1,197.5664	$1,197.57	$1,197.60	$1,197.60