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	$73.52	11.372%	$81.8807	$81.88	$81.90	$81.90
Purchase #2	$178.45	5.428%	$188.1363	$188.14	$188.15	$188.10
Purchase #3	$38.74	5.256%	$40.7762	$40.78	$40.80	$40.80
Purchase #4	$48.56	13.749%	$55.2365	$55.24	$55.25	$55.20
Purchase #5	$188.59	8.322%	$204.2845	$204.28	$204.30	$204.30
Purchase #6	$204.31	9.167%	$223.0391	$223.04	$223.05	$223.00
Purchase #7	$141.87	10.133%	$156.2457	$156.25	$156.25	$156.20
7 purchase totals =	$874.04		$949.5990	$949.61	$949.70	$949.50