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	$168.33	12.209%	$188.8814	$188.88	$188.90	$188.90
Purchase #2	$59.43	3.183%	$61.3217	$61.32	$61.30	$61.30
Purchase #3	$44.29	12.375%	$49.7709	$49.77	$49.75	$49.80
Purchase #4	$188.82	12.742%	$212.8794	$212.88	$212.90	$212.90
Purchase #5	$200.77	11.269%	$223.3948	$223.39	$223.40	$223.40
Purchase #6	$176.69	8.719%	$192.0956	$192.10	$192.10	$192.10
Purchase #7	$142.25	4.676%	$148.9016	$148.90	$148.90	$148.90
7 purchase totals =	$980.58		$1,077.2454	$1,077.24	$1,077.25	$1,077.30