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	$130.94	10.449%	$144.6219	$144.62	$144.60	$144.60
Purchase #2	$92.73	9.278%	$101.3335	$101.33	$101.35	$101.30
Purchase #3	$117.55	8.431%	$127.4606	$127.46	$127.45	$127.50
Purchase #4	$158.36	5.787%	$167.5243	$167.52	$167.50	$167.50
Purchase #5	$99.64	5.616%	$105.2358	$105.24	$105.25	$105.20
Purchase #6	$218.93	3.851%	$227.361	$227.36	$227.35	$227.40
Purchase #7	$195.58	5.274%	$205.8949	$205.89	$205.90	$205.90
7 purchase totals =	$1,013.73		$1,079.4320	$1,079.42	$1,079.40	$1,079.40