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	$214.74	6.227%	$228.1119	$228.11	$228.10	$228.10
Purchase #2	$164.85	5.618%	$174.1113	$174.11	$174.10	$174.10
Purchase #3	$216.52	12.171%	$242.8726	$242.87	$242.85	$242.90
Purchase #4	$65.67	9.764%	$72.082	$72.08	$72.10	$72.10
Purchase #5	$64.83	4.847%	$67.9723	$67.97	$67.95	$68.00
Purchase #6	$64.84	3.808%	$67.3091	$67.31	$67.30	$67.30
Purchase #7	$80.73	12.186%	$90.5678	$90.57	$90.55	$90.60
7 purchase totals =	$872.18		$943.0270	$943.02	$942.95	$943.10