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	$212.47	6.865%	$227.0561	$227.06	$227.05	$227.10
Purchase #2	$82.98	7.734%	$89.3977	$89.40	$89.40	$89.40
Purchase #3	$175.40	9.759%	$192.5173	$192.52	$192.50	$192.50
Purchase #4	$91.94	6.483%	$97.9005	$97.90	$97.90	$97.90
Purchase #5	$165.68	4.461%	$173.071	$173.07	$173.05	$173.10
Purchase #6	$48.31	9.629%	$52.9618	$52.96	$52.95	$53.00
Purchase #7	$7.77	8.824%	$8.4556	$8.46	$8.45	$8.50
7 purchase totals =	$784.55		$841.3600	$841.37	$841.30	$841.50