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	$129.90	4.488%	$135.7299	$135.73	$135.75	$135.70
Purchase #2	$186.43	13.622%	$211.8255	$211.83	$211.85	$211.80
Purchase #3	$31.38	11.616%	$35.0251	$35.03	$35.05	$35.00
Purchase #4	$238.27	13.153%	$269.6097	$269.61	$269.60	$269.60
Purchase #5	$171.72	5.483%	$181.1354	$181.14	$181.15	$181.10
Purchase #6	$126.45	10.687%	$139.9637	$139.96	$139.95	$140.00
Purchase #7	$86.28	4.293%	$89.984	$89.98	$90.00	$90.00
7 purchase totals =	$970.43		$1,063.2733	$1,063.28	$1,063.35	$1,063.20