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	$60.50	4.143%	$63.0065	$63.01	$63.00	$63.00
Purchase #2	$18.41	13.842%	$20.9583	$20.96	$20.95	$21.00
Purchase #3	$83.55	8.223%	$90.4203	$90.42	$90.40	$90.40
Purchase #4	$94.64	9.741%	$103.8589	$103.86	$103.85	$103.90
Purchase #5	$204.71	9.860%	$224.8944	$224.89	$224.90	$224.90
Purchase #6	$114.28	8.817%	$124.3561	$124.36	$124.35	$124.40
Purchase #7	$101.70	7.262%	$109.0855	$109.09	$109.10	$109.10
7 purchase totals =	$677.79		$736.5800	$736.59	$736.55	$736.70