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	$148.27	8.194%	$160.4192	$160.42	$160.40	$160.40
Purchase #2	$242.69	13.184%	$274.6862	$274.69	$274.70	$274.70
Purchase #3	$168.85	3.631%	$174.9809	$174.98	$175.00	$175.00
Purchase #4	$213.68	4.623%	$223.5584	$223.56	$223.55	$223.60
Purchase #5	$99.85	3.351%	$103.196	$103.20	$103.20	$103.20
Purchase #6	$73.61	9.702%	$80.7516	$80.75	$80.75	$80.80
Purchase #7	$11.77	4.220%	$12.2667	$12.27	$12.25	$12.30
7 purchase totals =	$958.72		$1,029.8590	$1,029.87	$1,029.85	$1,030.00