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	$171.65	10.298%	$189.3265	$189.33	$189.35	$189.30
Purchase #2	$215.51	3.443%	$222.93	$222.93	$222.95	$222.90
Purchase #3	$186.35	3.774%	$193.3828	$193.38	$193.40	$193.40
Purchase #4	$113.67	4.131%	$118.3657	$118.37	$118.35	$118.40
Purchase #5	$126.60	13.868%	$144.1569	$144.16	$144.15	$144.20
Purchase #6	$77.87	12.375%	$87.5064	$87.51	$87.50	$87.50
Purchase #7	$79.41	12.136%	$89.0472	$89.05	$89.05	$89.00
7 purchase totals =	$971.06		$1,044.7155	$1,044.73	$1,044.75	$1,044.70