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	$110.77	3.210%	$114.3257	$114.33	$114.35	$114.30
Purchase #2	$184.95	8.304%	$200.3082	$200.31	$200.30	$200.30
Purchase #3	$103.60	4.740%	$108.5106	$108.51	$108.50	$108.50
Purchase #4	$123.59	10.732%	$136.8537	$136.85	$136.85	$136.90
Purchase #5	$35.27	5.582%	$37.2388	$37.24	$37.25	$37.20
Purchase #6	$14.60	3.135%	$15.0577	$15.06	$15.05	$15.10
Purchase #7	$138.75	9.809%	$152.36	$152.36	$152.35	$152.40
7 purchase totals =	$711.53		$764.6547	$764.66	$764.65	$764.70