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	$173.35	3.582%	$179.5594	$179.56	$179.55	$179.60
Purchase #2	$96.73	4.102%	$100.6979	$100.70	$100.70	$100.70
Purchase #3	$41.79	8.712%	$45.4307	$45.43	$45.45	$45.40
Purchase #4	$213.55	10.859%	$236.7394	$236.74	$236.75	$236.70
Purchase #5	$121.40	4.709%	$127.1167	$127.12	$127.10	$127.10
Purchase #6	$215.61	3.439%	$223.0248	$223.02	$223.00	$223.00
Purchase #7	$105.36	12.566%	$118.5995	$118.60	$118.60	$118.60
7 purchase totals =	$967.79		$1,031.1684	$1,031.17	$1,031.15	$1,031.10