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	$70.68	9.808%	$77.6123	$77.61	$77.60	$77.60
Purchase #2	$101.43	8.486%	$110.0373	$110.04	$110.05	$110.00
Purchase #3	$188.45	4.147%	$196.265	$196.27	$196.25	$196.30
Purchase #4	$128.72	9.283%	$140.6691	$140.67	$140.65	$140.70
Purchase #5	$160.40	8.864%	$174.6179	$174.62	$174.60	$174.60
Purchase #6	$112.93	13.321%	$127.9734	$127.97	$127.95	$128.00
Purchase #7	$48.54	11.471%	$54.108	$54.11	$54.10	$54.10
7 purchase totals =	$811.15		$881.2830	$881.29	$881.20	$881.30