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	$220.82	6.477%	$235.1225	$235.12	$235.10	$235.10
Purchase #2	$149.92	8.573%	$162.7726	$162.77	$162.75	$162.80
Purchase #3	$19.42	3.617%	$20.1224	$20.12	$20.10	$20.10
Purchase #4	$192.95	12.200%	$216.4899	$216.49	$216.50	$216.50
Purchase #5	$49.34	8.542%	$53.5546	$53.55	$53.55	$53.60
Purchase #6	$39.49	7.282%	$42.3657	$42.37	$42.35	$42.40
Purchase #7	$40.88	7.346%	$43.883	$43.88	$43.90	$43.90
7 purchase totals =	$712.82		$774.3107	$774.30	$774.25	$774.40