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	$44.73	6.114%	$47.4648	$47.46	$47.45	$47.50
Purchase #2	$96.42	3.474%	$99.7696	$99.77	$99.75	$99.80
Purchase #3	$122.96	3.474%	$127.2316	$127.23	$127.25	$127.20
Purchase #4	$190.72	8.518%	$206.9655	$206.97	$206.95	$207.00
Purchase #5	$158.72	5.666%	$167.7131	$167.71	$167.70	$167.70
Purchase #6	$156.54	11.719%	$174.8849	$174.88	$174.90	$174.90
Purchase #7	$100.38	10.659%	$111.0795	$111.08	$111.10	$111.10
7 purchase totals =	$870.47		$935.1090	$935.10	$935.10	$935.20