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	$49.83	13.530%	$56.572	$56.57	$56.55	$56.60
Purchase #2	$136.53	8.236%	$147.7746	$147.77	$147.75	$147.80
Purchase #3	$114.78	10.740%	$127.1074	$127.11	$127.10	$127.10
Purchase #4	$95.64	7.707%	$103.011	$103.01	$103.00	$103.00
Purchase #5	$189.63	13.855%	$215.9032	$215.90	$215.90	$215.90
Purchase #6	$178.99	6.468%	$190.5671	$190.57	$190.55	$190.60
Purchase #7	$207.99	7.700%	$224.0052	$224.01	$224.00	$224.00
7 purchase totals =	$973.39		$1,064.9405	$1,064.94	$1,064.85	$1,065.00