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	$100.64	11.395%	$112.1079	$112.11	$112.10	$112.10
Purchase #2	$166.94	7.353%	$179.2151	$179.22	$179.20	$179.20
Purchase #3	$131.86	8.368%	$142.894	$142.89	$142.90	$142.90
Purchase #4	$114.65	10.786%	$127.0161	$127.02	$127.00	$127.00
Purchase #5	$230.37	5.760%	$243.6393	$243.64	$243.65	$243.60
Purchase #6	$88.91	3.710%	$92.2086	$92.21	$92.20	$92.20
Purchase #7	$194.91	7.158%	$208.8617	$208.86	$208.85	$208.90
7 purchase totals =	$1,028.28		$1,105.9427	$1,105.95	$1,105.90	$1,105.90