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	$223.33	5.400%	$235.3898	$235.39	$235.40	$235.40
Purchase #2	$54.60	8.824%	$59.4179	$59.42	$59.40	$59.40
Purchase #3	$103.58	13.166%	$117.2173	$117.22	$117.20	$117.20
Purchase #4	$79.35	12.194%	$89.0259	$89.03	$89.05	$89.00
Purchase #5	$167.77	6.730%	$179.0609	$179.06	$179.05	$179.10
Purchase #6	$201.81	4.137%	$210.1589	$210.16	$210.15	$210.20
Purchase #7	$91.40	8.120%	$98.8217	$98.82	$98.80	$98.80
7 purchase totals =	$921.84		$989.0924	$989.10	$989.05	$989.10