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	$191.70	11.212%	$213.1934	$213.19	$213.20	$213.20
Purchase #2	$101.31	9.170%	$110.6001	$110.60	$110.60	$110.60
Purchase #3	$240.45	4.138%	$250.3998	$250.40	$250.40	$250.40
Purchase #4	$51.54	7.135%	$55.2174	$55.22	$55.20	$55.20
Purchase #5	$212.55	13.577%	$241.4079	$241.41	$241.40	$241.40
Purchase #6	$110.95	5.172%	$116.6883	$116.69	$116.70	$116.70
Purchase #7	$91.32	8.531%	$99.1105	$99.11	$99.10	$99.10
7 purchase totals =	$999.82		$1,086.6174	$1,086.62	$1,086.60	$1,086.60