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	$158.43	10.862%	$175.6387	$175.64	$175.65	$175.60
Purchase #2	$179.57	3.768%	$186.3362	$186.34	$186.35	$186.30
Purchase #3	$174.88	10.848%	$193.851	$193.85	$193.85	$193.90
Purchase #4	$98.82	12.432%	$111.1053	$111.11	$111.10	$111.10
Purchase #5	$112.89	3.313%	$116.63	$116.63	$116.65	$116.60
Purchase #6	$112.37	11.449%	$125.2352	$125.24	$125.25	$125.20
Purchase #7	$66.50	7.870%	$71.7336	$71.73	$71.75	$71.70
7 purchase totals =	$903.46		$980.5300	$980.54	$980.60	$980.40