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	$213.31	4.760%	$223.4636	$223.46	$223.45	$223.50
Purchase #2	$214.59	6.626%	$228.8087	$228.81	$228.80	$228.80
Purchase #3	$181.97	7.872%	$196.2947	$196.29	$196.30	$196.30
Purchase #4	$44.28	9.300%	$48.398	$48.40	$48.40	$48.40
Purchase #5	$52.71	7.300%	$56.5578	$56.56	$56.55	$56.60
Purchase #6	$125.32	8.151%	$135.5348	$135.53	$135.55	$135.50
Purchase #7	$207.97	9.827%	$228.4072	$228.41	$228.40	$228.40
7 purchase totals =	$1,040.15		$1,117.4648	$1,117.46	$1,117.45	$1,117.50