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	$158.54	10.122%	$174.5874	$174.59	$174.60	$174.60
Purchase #2	$41.91	11.201%	$46.6043	$46.60	$46.60	$46.60
Purchase #3	$148.35	4.518%	$155.0525	$155.05	$155.05	$155.10
Purchase #4	$162.88	3.683%	$168.8789	$168.88	$168.90	$168.90
Purchase #5	$172.76	13.842%	$196.6734	$196.67	$196.65	$196.70
Purchase #6	$92.51	5.216%	$97.3353	$97.34	$97.35	$97.30
Purchase #7	$242.77	12.851%	$273.9684	$273.97	$273.95	$274.00
7 purchase totals =	$1,019.72		$1,113.1002	$1,113.10	$1,113.10	$1,113.20