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	$73.94	11.704%	$82.5939	$82.59	$82.60	$82.60
Purchase #2	$216.81	3.371%	$224.1187	$224.12	$224.10	$224.10
Purchase #3	$123.64	7.148%	$132.4778	$132.48	$132.50	$132.50
Purchase #4	$98.87	11.394%	$110.1352	$110.14	$110.15	$110.10
Purchase #5	$196.36	13.289%	$222.4543	$222.45	$222.45	$222.50
Purchase #6	$243.74	11.482%	$271.7262	$271.73	$271.75	$271.70
Purchase #7	$172.79	9.801%	$189.7251	$189.73	$189.75	$189.70
7 purchase totals =	$1,126.15		$1,233.2312	$1,233.24	$1,233.30	$1,233.20