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	$100.69	11.189%	$111.9562	$111.96	$111.95	$112.00
Purchase #2	$109.91	6.807%	$117.3916	$117.39	$117.40	$117.40
Purchase #3	$200.28	11.777%	$223.867	$223.87	$223.85	$223.90
Purchase #4	$53.88	9.736%	$59.1258	$59.13	$59.15	$59.10
Purchase #5	$49.53	3.694%	$51.3596	$51.36	$51.35	$51.40
Purchase #6	$109.74	10.146%	$120.8742	$120.87	$120.85	$120.90
Purchase #7	$152.59	5.450%	$160.9062	$160.91	$160.90	$160.90
7 purchase totals =	$776.62		$845.4806	$845.49	$845.45	$845.60