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	$112.88	9.463%	$123.5618	$123.56	$123.55	$123.60
Purchase #2	$151.38	6.755%	$161.6057	$161.61	$161.60	$161.60
Purchase #3	$84.34	11.693%	$94.2019	$94.20	$94.20	$94.20
Purchase #4	$165.60	12.451%	$186.2189	$186.22	$186.20	$186.20
Purchase #5	$98.57	10.867%	$109.2816	$109.28	$109.30	$109.30
Purchase #6	$149.83	8.773%	$162.9746	$162.97	$162.95	$163.00
Purchase #7	$173.82	4.444%	$181.5446	$181.54	$181.55	$181.50
7 purchase totals =	$936.42		$1,019.3891	$1,019.38	$1,019.35	$1,019.40