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	$116.72	5.463%	$123.0964	$123.10	$123.10	$123.10
Purchase #2	$102.41	7.159%	$109.7415	$109.74	$109.75	$109.70
Purchase #3	$57.59	3.546%	$59.6321	$59.63	$59.65	$59.60
Purchase #4	$213.91	13.857%	$243.5515	$243.55	$243.55	$243.60
Purchase #5	$242.25	8.356%	$262.4924	$262.49	$262.50	$262.50
Purchase #6	$106.65	10.415%	$117.7576	$117.76	$117.75	$117.80
Purchase #7	$136.34	10.171%	$150.2071	$150.21	$150.20	$150.20
7 purchase totals =	$975.87		$1,066.4786	$1,066.48	$1,066.50	$1,066.50