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	$91.96	7.529%	$98.8837	$98.88	$98.90	$98.90
Purchase #2	$37.56	6.228%	$39.8992	$39.90	$39.90	$39.90
Purchase #3	$70.44	13.776%	$80.1438	$80.14	$80.15	$80.10
Purchase #4	$229.89	11.758%	$256.9205	$256.92	$256.90	$256.90
Purchase #5	$102.85	8.490%	$111.582	$111.58	$111.60	$111.60
Purchase #6	$175.99	3.724%	$182.5439	$182.54	$182.55	$182.50
Purchase #7	$178.33	7.553%	$191.7993	$191.80	$191.80	$191.80
7 purchase totals =	$887.02		$961.7724	$961.76	$961.80	$961.70