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	$215.64	10.752%	$238.8256	$238.83	$238.85	$238.80
Purchase #2	$55.73	7.458%	$59.8863	$59.89	$59.90	$59.90
Purchase #3	$12.85	10.401%	$14.1865	$14.19	$14.20	$14.20
Purchase #4	$39.89	10.654%	$44.1399	$44.14	$44.15	$44.10
Purchase #5	$193.64	13.276%	$219.3476	$219.35	$219.35	$219.30
Purchase #6	$73.94	12.698%	$83.3289	$83.33	$83.35	$83.30
Purchase #7	$111.84	11.305%	$124.4835	$124.48	$124.50	$124.50
7 purchase totals =	$703.53		$784.1983	$784.21	$784.30	$784.10