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	$239.72	9.663%	$262.8841	$262.88	$262.90	$262.90
Purchase #2	$111.84	5.640%	$118.1478	$118.15	$118.15	$118.10
Purchase #3	$129.96	4.446%	$135.738	$135.74	$135.75	$135.70
Purchase #4	$90.52	11.514%	$100.9425	$100.94	$100.95	$100.90
Purchase #5	$32.56	10.378%	$35.9391	$35.94	$35.95	$35.90
Purchase #6	$153.75	11.479%	$171.399	$171.40	$171.40	$171.40
Purchase #7	$97.75	13.627%	$111.0704	$111.07	$111.05	$111.10
7 purchase totals =	$856.10		$936.1209	$936.12	$936.15	$936.00