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	$144.59	13.865%	$164.6374	$164.64	$164.65	$164.60
Purchase #2	$178.30	11.127%	$198.1394	$198.14	$198.15	$198.10
Purchase #3	$37.29	7.611%	$40.1281	$40.13	$40.15	$40.10
Purchase #4	$230.75	5.612%	$243.6997	$243.70	$243.70	$243.70
Purchase #5	$197.96	13.125%	$223.9423	$223.94	$223.95	$223.90
Purchase #6	$125.99	4.209%	$131.2929	$131.29	$131.30	$131.30
Purchase #7	$156.73	6.298%	$166.6009	$166.60	$166.60	$166.60
7 purchase totals =	$1,071.61		$1,168.4407	$1,168.44	$1,168.50	$1,168.30