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	$72.96	7.271%	$78.2649	$78.26	$78.25	$78.30
Purchase #2	$182.25	12.380%	$204.8126	$204.81	$204.80	$204.80
Purchase #3	$64.26	4.444%	$67.1157	$67.12	$67.10	$67.10
Purchase #4	$242.35	3.199%	$250.1028	$250.10	$250.10	$250.10
Purchase #5	$114.54	11.396%	$127.593	$127.59	$127.60	$127.60
Purchase #6	$43.61	13.455%	$49.4777	$49.48	$49.50	$49.50
Purchase #7	$173.31	7.269%	$185.9079	$185.91	$185.90	$185.90
7 purchase totals =	$893.28		$963.2746	$963.27	$963.25	$963.30