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	$187.88	12.747%	$211.8291	$211.83	$211.85	$211.80
Purchase #2	$100.66	11.201%	$111.9349	$111.93	$111.95	$111.90
Purchase #3	$127.99	11.267%	$142.4106	$142.41	$142.40	$142.40
Purchase #4	$38.61	11.779%	$43.1579	$43.16	$43.15	$43.20
Purchase #5	$60.91	3.210%	$62.8652	$62.87	$62.85	$62.90
Purchase #6	$231.86	7.721%	$249.7619	$249.76	$249.75	$249.80
Purchase #7	$179.75	9.758%	$197.29	$197.29	$197.30	$197.30
7 purchase totals =	$927.66		$1,019.2496	$1,019.25	$1,019.25	$1,019.30