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	$91.35	7.345%	$98.0597	$98.06	$98.05	$98.10
Purchase #2	$26.75	6.380%	$28.4567	$28.46	$28.45	$28.50
Purchase #3	$59.35	13.223%	$67.1979	$67.20	$67.20	$67.20
Purchase #4	$78.91	8.783%	$85.8407	$85.84	$85.85	$85.80
Purchase #5	$86.51	9.257%	$94.5182	$94.52	$94.50	$94.50
Purchase #6	$106.59	11.677%	$119.0365	$119.04	$119.05	$119.00
Purchase #7	$40.33	3.872%	$41.8916	$41.89	$41.90	$41.90
7 purchase totals =	$489.79		$535.0013	$535.01	$535.00	$535.00