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	$74.55	4.776%	$78.1105	$78.11	$78.10	$78.10
Purchase #2	$242.33	7.715%	$261.0258	$261.03	$261.05	$261.00
Purchase #3	$136.70	5.722%	$144.522	$144.52	$144.50	$144.50
Purchase #4	$105.38	11.138%	$117.1172	$117.12	$117.10	$117.10
Purchase #5	$65.56	4.307%	$68.3837	$68.38	$68.40	$68.40
Purchase #6	$229.27	4.694%	$240.0319	$240.03	$240.05	$240.00
Purchase #7	$144.52	6.484%	$153.8907	$153.89	$153.90	$153.90
7 purchase totals =	$998.31		$1,063.0818	$1,063.08	$1,063.10	$1,063.00