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	$232.41	5.354%	$244.8532	$244.85	$244.85	$244.90
Purchase #2	$228.72	4.196%	$238.3171	$238.32	$238.30	$238.30
Purchase #3	$35.61	12.417%	$40.0317	$40.03	$40.05	$40.00
Purchase #4	$104.34	13.344%	$118.2631	$118.26	$118.25	$118.30
Purchase #5	$90.68	7.471%	$97.4547	$97.45	$97.45	$97.50
Purchase #6	$196.80	10.525%	$217.5132	$217.51	$217.50	$217.50
Purchase #7	$96.54	9.288%	$105.5066	$105.51	$105.50	$105.50
7 purchase totals =	$985.10		$1,061.9396	$1,061.93	$1,061.90	$1,062.00