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	$108.66	13.828%	$123.6855	$123.69	$123.70	$123.70
Purchase #2	$10.33	5.514%	$10.8996	$10.90	$10.90	$10.90
Purchase #3	$96.31	5.695%	$101.7949	$101.79	$101.80	$101.80
Purchase #4	$212.78	12.815%	$240.0478	$240.05	$240.05	$240.00
Purchase #5	$228.76	5.187%	$240.6258	$240.63	$240.65	$240.60
Purchase #6	$192.27	3.131%	$198.29	$198.29	$198.30	$198.30
Purchase #7	$128.37	11.486%	$143.1146	$143.11	$143.10	$143.10
7 purchase totals =	$977.48		$1,058.4582	$1,058.46	$1,058.50	$1,058.40