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	$205.71	8.649%	$223.5019	$223.50	$223.50	$223.50
Purchase #2	$67.91	5.122%	$71.3884	$71.39	$71.40	$71.40
Purchase #3	$179.85	11.523%	$200.5741	$200.57	$200.55	$200.60
Purchase #4	$56.32	12.580%	$63.4051	$63.41	$63.40	$63.40
Purchase #5	$57.75	9.299%	$63.1202	$63.12	$63.10	$63.10
Purchase #6	$198.82	10.303%	$219.3044	$219.30	$219.30	$219.30
Purchase #7	$240.26	7.856%	$259.1348	$259.13	$259.15	$259.10
7 purchase totals =	$1,006.62		$1,100.4289	$1,100.42	$1,100.40	$1,100.40