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	$35.81	13.523%	$40.6526	$40.65	$40.65	$40.70
Purchase #2	$36.60	13.726%	$41.6237	$41.62	$41.60	$41.60
Purchase #3	$135.53	9.368%	$148.2265	$148.23	$148.25	$148.20
Purchase #4	$186.71	13.127%	$211.2194	$211.22	$211.20	$211.20
Purchase #5	$248.44	3.133%	$256.2236	$256.22	$256.20	$256.20
Purchase #6	$245.39	9.597%	$268.9401	$268.94	$268.95	$268.90
Purchase #7	$130.76	10.693%	$144.7422	$144.74	$144.75	$144.70
7 purchase totals =	$1,019.24		$1,111.6281	$1,111.62	$1,111.60	$1,111.50