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	$107.32	4.263%	$111.8951	$111.90	$111.90	$111.90
Purchase #2	$111.65	3.124%	$115.1379	$115.14	$115.15	$115.10
Purchase #3	$157.77	6.277%	$167.6732	$167.67	$167.65	$167.70
Purchase #4	$83.63	5.872%	$88.5408	$88.54	$88.55	$88.50
Purchase #5	$243.43	13.521%	$276.3442	$276.34	$276.35	$276.30
Purchase #6	$64.47	11.621%	$71.9621	$71.96	$71.95	$72.00
Purchase #7	$97.48	4.206%	$101.58	$101.58	$101.60	$101.60
7 purchase totals =	$865.75		$933.1333	$933.13	$933.15	$933.10