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	$121.90	4.148%	$126.9564	$126.96	$126.95	$127.00
Purchase #2	$41.43	9.499%	$45.3654	$45.37	$45.35	$45.40
Purchase #3	$98.83	7.149%	$105.8954	$105.90	$105.90	$105.90
Purchase #4	$250.67	9.359%	$274.1302	$274.13	$274.15	$274.10
Purchase #5	$223.56	3.861%	$232.1917	$232.19	$232.20	$232.20
Purchase #6	$12.94	5.604%	$13.6652	$13.67	$13.65	$13.70
Purchase #7	$244.56	9.632%	$268.116	$268.12	$268.10	$268.10
7 purchase totals =	$993.89		$1,066.3203	$1,066.34	$1,066.30	$1,066.40