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	$88.66	8.688%	$96.3628	$96.36	$96.35	$96.40
Purchase #2	$85.56	3.597%	$88.6376	$88.64	$88.65	$88.60
Purchase #3	$169.63	3.535%	$175.6264	$175.63	$175.65	$175.60
Purchase #4	$81.40	9.635%	$89.2429	$89.24	$89.25	$89.20
Purchase #5	$222.66	6.198%	$236.4605	$236.46	$236.45	$236.50
Purchase #6	$64.34	13.119%	$72.7808	$72.78	$72.80	$72.80
Purchase #7	$201.59	4.720%	$211.105	$211.11	$211.10	$211.10
7 purchase totals =	$913.84		$970.2160	$970.22	$970.25	$970.20