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	$122.82	5.280%	$129.3049	$129.30	$129.30	$129.30
Purchase #2	$138.56	4.507%	$144.8049	$144.80	$144.80	$144.80
Purchase #3	$196.38	13.873%	$223.6238	$223.62	$223.60	$223.60
Purchase #4	$153.64	3.429%	$158.9083	$158.91	$158.90	$158.90
Purchase #5	$179.56	11.107%	$199.5037	$199.50	$199.50	$199.50
Purchase #6	$173.72	11.577%	$193.8316	$193.83	$193.85	$193.80
Purchase #7	$97.79	5.776%	$103.4384	$103.44	$103.45	$103.40
7 purchase totals =	$1,062.47		$1,153.4156	$1,153.40	$1,153.40	$1,153.30