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	$70.92	10.160%	$78.1255	$78.13	$78.15	$78.10
Purchase #2	$240.32	13.333%	$272.3619	$272.36	$272.35	$272.40
Purchase #3	$168.82	4.289%	$176.0607	$176.06	$176.05	$176.10
Purchase #4	$196.58	10.319%	$216.8651	$216.87	$216.85	$216.90
Purchase #5	$40.47	12.554%	$45.5506	$45.55	$45.55	$45.60
Purchase #6	$25.33	9.763%	$27.803	$27.80	$27.80	$27.80
Purchase #7	$182.71	13.477%	$207.3338	$207.33	$207.35	$207.30
7 purchase totals =	$925.15		$1,024.1006	$1,024.10	$1,024.10	$1,024.20