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	$67.83	4.858%	$71.1252	$71.13	$71.15	$71.10
Purchase #2	$39.71	6.548%	$42.3102	$42.31	$42.30	$42.30
Purchase #3	$220.61	3.335%	$227.9673	$227.97	$227.95	$228.00
Purchase #4	$202.28	10.713%	$223.9503	$223.95	$223.95	$224.00
Purchase #5	$83.94	6.390%	$89.3038	$89.30	$89.30	$89.30
Purchase #6	$211.49	5.615%	$223.3652	$223.37	$223.35	$223.40
Purchase #7	$129.76	7.312%	$139.2481	$139.25	$139.25	$139.20
7 purchase totals =	$955.62		$1,017.2701	$1,017.28	$1,017.25	$1,017.30