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	$53.72	13.650%	$61.0528	$61.05	$61.05	$61.10
Purchase #2	$51.74	3.276%	$53.435	$53.44	$53.45	$53.40
Purchase #3	$33.84	13.211%	$38.3106	$38.31	$38.30	$38.30
Purchase #4	$206.64	7.461%	$222.0574	$222.06	$222.05	$222.10
Purchase #5	$249.75	12.318%	$280.5142	$280.51	$280.50	$280.50
Purchase #6	$5.64	10.830%	$6.2508	$6.25	$6.25	$6.30
Purchase #7	$82.65	4.167%	$86.094	$86.09	$86.10	$86.10
7 purchase totals =	$683.98		$747.7148	$747.71	$747.70	$747.80