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	$184.93	7.717%	$199.201	$199.20	$199.20	$199.20
Purchase #2	$75.78	5.448%	$79.9085	$79.91	$79.90	$79.90
Purchase #3	$40.37	7.262%	$43.3017	$43.30	$43.30	$43.30
Purchase #4	$31.89	11.678%	$35.6141	$35.61	$35.60	$35.60
Purchase #5	$182.33	12.111%	$204.412	$204.41	$204.40	$204.40
Purchase #6	$19.31	13.426%	$21.9026	$21.90	$21.90	$21.90
Purchase #7	$167.72	12.676%	$188.9802	$188.98	$189.00	$189.00
7 purchase totals =	$702.33		$773.3201	$773.31	$773.30	$773.30