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	$57.53	6.814%	$61.4501	$61.45	$61.45	$61.50
Purchase #2	$86.54	9.790%	$95.0123	$95.01	$95.00	$95.00
Purchase #3	$48.78	11.714%	$54.4941	$54.49	$54.50	$54.50
Purchase #4	$52.73	3.858%	$54.7643	$54.76	$54.75	$54.80
Purchase #5	$168.89	3.320%	$174.4971	$174.50	$174.50	$174.50
Purchase #6	$45.95	11.262%	$51.1249	$51.12	$51.10	$51.10
Purchase #7	$185.78	11.847%	$207.7894	$207.79	$207.80	$207.80
7 purchase totals =	$646.20		$699.1322	$699.12	$699.10	$699.20