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	$204.69	13.446%	$232.2126	$232.21	$232.20	$232.20
Purchase #2	$141.89	6.793%	$151.5286	$151.53	$151.55	$151.50
Purchase #3	$69.41	13.528%	$78.7998	$78.80	$78.80	$78.80
Purchase #4	$53.87	10.502%	$59.5274	$59.53	$59.55	$59.50
Purchase #5	$230.65	4.232%	$240.4111	$240.41	$240.40	$240.40
Purchase #6	$171.64	4.783%	$179.8495	$179.85	$179.85	$179.80
Purchase #7	$78.97	4.516%	$82.5363	$82.54	$82.55	$82.50
7 purchase totals =	$951.12		$1,024.8653	$1,024.87	$1,024.90	$1,024.70