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	$54.41	3.565%	$56.3497	$56.35	$56.35	$56.30
Purchase #2	$57.48	10.712%	$63.6373	$63.64	$63.65	$63.60
Purchase #3	$106.81	4.845%	$111.9849	$111.98	$112.00	$112.00
Purchase #4	$64.28	5.605%	$67.8829	$67.88	$67.90	$67.90
Purchase #5	$98.74	4.731%	$103.4114	$103.41	$103.40	$103.40
Purchase #6	$167.52	4.173%	$174.5106	$174.51	$174.50	$174.50
Purchase #7	$154.29	11.254%	$171.6538	$171.65	$171.65	$171.70
7 purchase totals =	$703.53		$749.4306	$749.42	$749.45	$749.40