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	$101.76	7.516%	$109.4083	$109.41	$109.40	$109.40
Purchase #2	$40.81	3.729%	$42.3318	$42.33	$42.35	$42.30
Purchase #3	$51.29	9.469%	$56.1467	$56.15	$56.15	$56.10
Purchase #4	$162.85	10.104%	$179.3044	$179.30	$179.30	$179.30
Purchase #5	$213.95	11.599%	$238.7661	$238.77	$238.75	$238.80
Purchase #6	$236.56	3.510%	$244.8633	$244.86	$244.85	$244.90
Purchase #7	$167.84	13.807%	$191.0137	$191.01	$191.00	$191.00
7 purchase totals =	$975.06		$1,061.8343	$1,061.83	$1,061.80	$1,061.80