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	$123.27	11.333%	$137.2402	$137.24	$137.25	$137.20
Purchase #2	$73.63	6.842%	$78.6678	$78.67	$78.65	$78.70
Purchase #3	$134.77	10.158%	$148.4599	$148.46	$148.45	$148.50
Purchase #4	$8.65	11.279%	$9.6256	$9.63	$9.65	$9.60
Purchase #5	$201.91	10.561%	$223.2337	$223.23	$223.25	$223.20
Purchase #6	$83.40	7.381%	$89.5558	$89.56	$89.55	$89.60
Purchase #7	$44.61	10.583%	$49.3311	$49.33	$49.35	$49.30
7 purchase totals =	$670.24		$736.1141	$736.12	$736.15	$736.10