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	$110.89	7.157%	$118.8264	$118.83	$118.85	$118.80
Purchase #2	$164.46	4.363%	$171.6354	$171.64	$171.65	$171.60
Purchase #3	$210.60	3.426%	$217.8152	$217.82	$217.80	$217.80
Purchase #4	$39.90	5.651%	$42.1547	$42.15	$42.15	$42.20
Purchase #5	$228.51	11.716%	$255.2822	$255.28	$255.30	$255.30
Purchase #6	$21.31	4.369%	$22.241	$22.24	$22.25	$22.20
Purchase #7	$179.98	8.798%	$195.8146	$195.81	$195.80	$195.80
7 purchase totals =	$955.65		$1,023.7695	$1,023.77	$1,023.80	$1,023.70