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	$83.96	7.432%	$90.1999	$90.20	$90.20	$90.20
Purchase #2	$229.61	5.317%	$241.8184	$241.82	$241.80	$241.80
Purchase #3	$47.53	12.128%	$53.2944	$53.29	$53.30	$53.30
Purchase #4	$207.70	11.271%	$231.1099	$231.11	$231.10	$231.10
Purchase #5	$119.56	7.316%	$128.307	$128.31	$128.30	$128.30
Purchase #6	$127.46	13.638%	$144.843	$144.84	$144.85	$144.80
Purchase #7	$129.66	13.685%	$147.404	$147.40	$147.40	$147.40
7 purchase totals =	$945.48		$1,036.9766	$1,036.97	$1,036.95	$1,036.90