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	$228.77	13.188%	$258.9402	$258.94	$258.95	$258.90
Purchase #2	$190.60	3.258%	$196.8097	$196.81	$196.80	$196.80
Purchase #3	$99.59	12.699%	$112.2369	$112.24	$112.25	$112.20
Purchase #4	$77.75	11.331%	$86.5599	$86.56	$86.55	$86.60
Purchase #5	$51.56	7.753%	$55.5574	$55.56	$55.55	$55.60
Purchase #6	$28.26	12.478%	$31.7863	$31.79	$31.80	$31.80
Purchase #7	$211.64	5.715%	$223.7352	$223.74	$223.75	$223.70
7 purchase totals =	$888.17		$965.6256	$965.64	$965.65	$965.60