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	$237.63	5.582%	$250.8945	$250.89	$250.90	$250.90
Purchase #2	$28.78	13.870%	$32.7718	$32.77	$32.75	$32.80
Purchase #3	$94.91	11.664%	$105.9803	$105.98	$106.00	$106.00
Purchase #4	$62.95	13.230%	$71.2783	$71.28	$71.30	$71.30
Purchase #5	$40.28	6.820%	$43.0271	$43.03	$43.05	$43.00
Purchase #6	$186.79	5.729%	$197.4912	$197.49	$197.50	$197.50
Purchase #7	$71.32	13.335%	$80.8305	$80.83	$80.85	$80.80
7 purchase totals =	$722.66		$782.2737	$782.27	$782.35	$782.30